cam gear timing

[twilightprotege]

this post has been edited by me. below is now correct information, but is still general. if you read through the thread you'll see how we got to this point. and make sure if you're reading this for the first time because you are getting cam gears and want to adjust the timing, GET SOME DYNO TIME!!!!

<b>advance intake cam only :</b> This will increase valve overlap. Will help with top end power
<b>retard intake cam only :</b> This will decrease valve overlap. Will help with bottom end power
<b>advance exhaust cam only :</b> This will decrease valve overlap. Will help with bottom end power
<b/>retard exhaust cam only :</b> This will increase valve overlap. Will help with bottom end power

so from the above, we can assume the following (hopefully)
<b>advance both intake and exhaust cam :</b> This will move the power band down in the rev range. Overlap will not change if degrees over advancement for both cams are the same. This will be apx 100rpm lower for every 2 degrees advancement
<b>retard both intake and exhaust cam :</b> This will move the power hand up in the rev range. Overlap will not change if degrees over advancement for both cams are the same. This will be apx 100rpm higher for every 2 degrees advancement

[viVid]

Twilight, this is good info! It has always seemed backwards to me that advancing yields more low end while retarding yeilds more top end. It seems like it should be the other way around! Until you think about it: when advancing the cam gear, you are turning the gear in the direction of motion (valves open later) and when retarding, you are turning the gear against the direction of motion (valves open sooner). Just thought I would put that out there just in case I am not the only retard here.

If my first grade math skills are still with me, that gives you an additional 4 degrees of overlap. Probably be a good starting point, but I am not sure you would want any more overlap than that. I have heard that these engines don't respond well to a lot of overlap because of the long stroke.

Keep us posted on your progress. I will be getting a set soon (missed out the the GB).

[p5sundevil]

sounds good, i like the advancing 2 degrees and both for NA operation and maybe increasing the amount of exhaust retarding for a boost application. Mid range is where I want my power.

[twilightprotege]

vivid - i beleive it's actually the other way around. advancing the cams means the valves open sooner and retarding means they open later. apparently the reason why advancing the timing yields more low end power is because the valve will be open move for the initial pull down of the piston, but the down side of that is that the valve isnt open for as long.
so advancing the intake cam and retarding the exhaust cam for what i said will actually decrease my valve overlap by 4 degrees, which is what i'm desparately needing

i know it sounds all strange, but think of it this way. you're turning the cam in relation to the rotation of the engine. so it's going in a clockwise direction. to advance the cam you're going from 1pm to 2pm, retarding from 2pm to 1pm. hope that's easy to understand

[Installshield 2]

Good info Andy, I think I may have reversed that in a few threads by accident...but can't remember...

Some of this is a bit confusing though...If retarding the intake cam and advancing the exhuast cam done seperately helps brings the power band down...how does advancing both together help bring the power down? I may be missing something...but see what I mean? the info seems to contradict itself...

[Installshield 2]

ah you posted while I was typing...nevermind the first part of the above post...

[twilightprotege]

oh hang on, i've got it around the wrong way. i've been inhaling too many car fumes today. damn me. that info above was taken straight from a cam gear site.

yeah it doesnt sound right to me. "advancing" to me means that something is going to be there sooner than normal...ie opening the valve sooner and closing it sooner.

i'll do some more lookig online and see if any other sites confirm what i've said in the first or my 2nd post...

[L8R]

no idea or comment hehe. just good information, thanks! - chris

[twilightprotege]

here's a bit of info from importtuner - http://www.importtuner.com/insidetechnology/0208it_insidetechnology/

says advancing is like what i said in my 2nd post. maybe my first post is wrong then???

[Installshield 2]

Originally posted by twilightprotege
oh hang on, i've got it around the wrong way. i've been inhaling too many car fumes today. damn me. that info above was taken straight from a cam gear site.

yeah it doesnt sound right to me. "advancing" to me means that something is going to be there sooner than normal...ie opening the valve sooner and closing it sooner.

i'll do some more lookig online and see if any other sites confirm what i've said in the first or my 2nd post...

ok man, we need to get as much info on this as we can to lay down an definative accurate thread...you started it off great, but some of the info gets really confusing and seems to contradict itself...I don't know the answers to some of this so I need all the help I can get...

I will start something off about "blow down" and some other exhaust related issues, and what they do to where the power band is located...

Blow Down: This refers to exhaust valve conditions in relation to the end of the compression stroke and beginning of the exhuast stroke...Blow Down is a condition that occurs when the exhaust valves open before BDC of the compression stroke...the exhaust valves open and allow the pressurized burned gasses to "vent" out of the chamber...this is also somewhat aided by vacuum conditions within the external exhaust piping...this is needed for a high rpm engine...It allows very little resistance on the exhaust stroke which helps with high rpm breathing and output...

Now a lack of blow down occurs when the valves do not open before BDC of the compression stroke...this can create pressure in the exhaust stroke...burned gasses will get squeezed before the valves are flung open...This only occurs if the valves don't open for a longer period of time after BDC of the compression stroke...This is better for low rpm power, in which none of the combustion pressures are vented out...the expansion of the air/fuel mixture is used fully to descend the piston, and nothing is vented until the cylinder is moving up again...this helps idle also...

So Andy I would say one thing that is occuring with you current setup is that you have too much blow down...The exhuast cam needs to open later than it currently is...this will help to allow each mixture expansion do what it's intended purpose is...

But I still don't really understand what advancing or retarding the cam does in relation to this...If retarding the exhaust cam makes the valves open sooner, you don't want that (this is what I think it does)...If advancing the exhaust cam makes the valves open sooner you don't want that either...the definition is what is confusing me...You want the exhuast valves to open a few degrees later, whether advancing or retarding the exhuast cam accomplishes that is up in the air to me currently...

[twilightprotege]

the easiest way i can think of it is like a clock. so the exhaust opens later i need to turn it back (retarding it).

i'm definately going to try turning back the exhaust cam - ie to the left about 4 degrees, and then turn the intake cam 2 degrees to the right. as far as i can work out, that will work.

it just sucks that every single time i type in anything to do with adjusting cam gears in google, yahoo etc, it's all for sale crap...

[Installshield 2]

Ok Andy, your link answered it I think...Advancing either cam creates the valves to be opened sooner and close sooner...Retarding either cam creates the valves to open later and close later...

So with that info, I would guess you need to retard the exhaust cam on your current setup for the reasons I posted above...so you were right all along with that...

[Installshield 2]

Originally posted by twilightprotege


it just sucks that every single time i type in anything to do with adjusting cam gears in google, yahoo etc, it's all for sale crap...

Oh I know man...98% of my search results were for people trying to sell shit...but after sifting through a lot of crap you sometimes find info you are looking for...just isn't as easy as it used to be...

[twilightprotege]

exactly.

i might go and change my initial thread. i dont think importtuner would be wrong...

here's another anyway - advance clockwise...retard anti-clockwise

http://www.acc-unlimited.com/product/detail/aadjcam.html

[twilightprotege]

initial post changed. sorry for the confusion guys. damn internet search engines!!! :mad:

[Installshield 2]

yeah maybe alter your first post a little...they claim that advancing BOTH cams brings the power back down, in which it doesn't always...

All this crap makes me want a set of adjustable cam gears immediately...

[twilightprotege]

hehehehehe...speak to propartsusa.com and see if you can still get the GB price!

yeah the initial post is very general. i just did the a copy paste.

<b>warning! anyone reading this, info here is general. it all depends on your setup of your engine...</b>

anyway, me thinks i should retard the exhaust cam more? like 4-6 degrees and the intake still advance 2deg. still anyway, once i can get on a dyno and get the engine really tuned...i cant wait to see what i can get outta the car

[Installshield 2]

woah man I think you adjusted the wrong thing on your first post...the initial post says that advancing the intake cam and exhuast cam the same amount brings power down, which will not always be the case on all DOHC engines...

it is accurate that advancing the intake cam and exhuast cam the same will keep the overlap the same though...so that part is right...

Also what you changed was right all along...retarding the exhuast cam will increase overlap if done alone...and advancing the intake cam will increase overlap if done alone...

[perfworks]

Well if you guys dont mind ill post some generic info for some others who may not understand some basics first then they can all join in the dialog.
They are some direct quotes from one of my distributors.
I'll cut and paste some of the info here.

QUOTE-

CAMSHAFT RULE #1-- Don't even think about buying a camshaft until you have taken care of your exhaust, heads, and induction FIRST. Otherwise, your new cam will only give you mediocre results at best.
In general, camshafts are NOT power makers. The camshaft is much more important for shaping and improving your torque curve than it is for making power. The camshaft "makes" power by determining where the engine makes its best power. Without ample breathing room around it (induction, heads, exhaust), the cam can do very little.
The camshaft "controls" engine breathing. It determines when the engine breathes, and (if the rest of the engine has been prepared for it) it controls how deeply the engine breathes. The camshaft also determines how well the engine "holds its breath." It determines at what speed the engine has the best volume of air/fuel mixture in the cylinders.

Long Duration cam, with lots of overlap, either loses fresh air/fuel mixture out the exhaust ports, or pushes exhaust up into the intake ports, at low speeds. But at high speeds it works to pack more fresh air/fuel mixture into the cylinders. Thus, more high-end power, but poor low-end street manners.
Short Duration cam, with less overlap, retains mixture well at low speeds, but can't allow the engine to breathe as well at high speeds. Thus, more low-end torque, but not much on the top end.
Lift, in general, increases torque and horsepower. But there is a limit. Heads flow best at a certain lift. Refer back to the "Heads" page and look at the Flow Bench chart. You'll see that my heads flow best between 0.4" and 0.5" of lift. To get the best flow, you want to lift the valves JUST BARELY HIGHER than the point of maximum flow. This way, the valve spends the most time possible at maximum lift, and passes the most mixture or exhaust possible. Believe it or not, you can lift the valves too high and actually hurt performance.
Selecting a camshaft can be a delicate process, and sometimes it seems more like magic than science.
Dyno2000 software helps make cam selection relatively easy. All you have to do is enter the specs on the cam you are considering, then let the software show you what the cam will do. When using Dyno2000, it's best to use "seat-to-seat" specs, rather than "0.050-lift" specs. With 0.050-lift specs, the software has to estimate the actual opening and closing points of the cam, and it's usually somewhat inaccurate. I want to know the "advertised" seat-to-seat specs.
For the street, you're looking for a cam that will produce loads of low-end torque along with a long, flat torque curve. The perfect cam for one engine won't necessarily work so well in another. The cam that I like for what I want to do probably won't be what you want.

[perfworks]

QUOTE-

No engine part is more vital, yet more misunderstood, than the camshaft. The camshaft is a long, lumpy, metal stick that is tied to the engine's crankshaft (by a chain, gears, or a belt). In fact, it's often called a "bump stick." It controls the opening and closing of the valves in the cylinder heads-- when they open; when they close; how fast they open; how fast they close; how high they open. Most engines have one camshaft. More and more engines have two. A few have four!
"When they open" and "when they close" determine what is called "valve timing." The difference between "when they open" and "when they close" is the valve's "duration." The "how high" is referred to as "lift."

The Very Basics
A bit more terminology is required before we can start getting technical. Refer to Figure 1 as I explain. Figure 1 is an "end-on" view of a single lobe of the camshaft.


Figure 1
/members/perfworks/lobe.gif
The camshaft is a straight metal shaft with bumps on it. The bumps are called lobes. The gray area in the picture is the shaft's "base circle." The blue area in the picture is the lobe. The area of the base circle opposite the lobe is the "heel." The tip of the lobe is called the "nose" or "toe." (Get it? Heel? Toe?) As the camshaft rotates, the engine's valve lifters (called "followers" in overhead cam engines) ride on the surface of the base circle and the lobes. When a lobe passes under the lifter, the lifter is pushed up. The lifter is connected to the top of a valve by various means (depending on the engine), and pushes the valve open.
Between the edges of the lobe and the heel are areas called "Clearance Ramps." These are places that are higher than the base circle, but only slightly. When the lifter is on the clearance ramps, it moves very slowly. The valve is not open enough to pass any significant amount of air or exhaust, but it is open. The clearance ramps are there to reduce forces on the valve train that could tear it apart or allow the valve to slam against its seat in the cylinder head.
The distance between the base circle and end of the toe is the lift. More specifically, as you will see later, it is called the "lift at camshaft."

[perfworks]

Valve timing
As the engine's crankshaft rotates, the pistons move up and down in the cylinders. The engine operates on 4 "strokes", two up or down motions per rotation of the crankshaft. Two full rotations of the crankshaft are required to complete a full cycle of 4 strokes.
On the first stroke (Intake), the piston moves down. As the piston moves down, the intake valve is open, allowing air/fuel mixture to enter the cylinder. The mixture is pushed into the cylinder by outside atmospheric pressure.
On the second stroke (Compression), the valves are closed. As the piston moves up in the cylinder the fuel/air mixture is compressed, in preparation for burning.
Near the point where the piston is all the way to the top of its travel, the spark plug fires, igniting the fuel/air mixture. On the third stroke (Power), the burning mixture pushes the piston back down. The valves are still closed.
On the fourth stroke (Exhaust), the exhaust valve opens, and the burnt gasses are pushed out through the open valve into the exhaust manifold. After this, the process starts all over again.
The timing of the intake and exhaust valves are critical during this 4-stroke process. It is not mechanically possible to snap the valves open at a precise moment. And since everything is moving at high speed-- all the parts, intake mixture, exhaust gasses-- the valve timing must "anticipate" the next stroke.
So, the intake valve opens a little bit before the start of the Intake stroke. The timing is set this way because by the time the mixture starts to move into the cylinder, the piston may have already moved past its Top Dead Center (TDC) position, and started moving down.
The intake valve closes a little bit after the start of the compression stroke. This is because the mixture has some speed built up as it is coming into the cylinder. This built up speed can actually pack more mixture into the cylinder at the last moment.
The exhaust valve opens a bit before the exhaust stroke actually starts. By this time, the mixture has finished burning, and it has expended about all the energy it can to piston. Opening the valve before Bottom Dead Center (BTC), lets some of the exhaust's pressure start pushing itself out of the cylinder, even before the piston starts moving up.
In the same way, the exhaust valve closes a little bit after the piston has passed TDC. This is because the moving exhaust gasses have some speed built up, and they can do more work for us as they blow out of the valve.
If you think about what I just said, that means there is a point where the intake valve and the exhaust valve are both a little bit open at the same time, between the end of the exhaust stroke and the beginning of the intake stroke. That extra work we can get from the exiting exhaust gas is this-- The exhaust has some speed built up, and it doesn't want to stop on its own. That is called "inertia." Inertia is the tendency of moving things to keep moving, and still things to remain still. Like the way your car coasts after you let off the gas.
The exhaust gasses are moving fast, and not wanting to slow down. This creates a partial vacuum in the combustion chamber as they exit. The intake valve is starting to open at the same time. The vacuum created by the fast-moving exhaust gasses, helps to start pulling the intake mixture into the cylinder for the next cycle.

The period when both valves are both a little bit open at the same time is called "overlap." Small overlap produces more torque at low engine speeds, but not so much at high speeds. Large overlap produces lower torque and low engine speeds, but more power as the engine runs faster.
As overlap is decreased, the engine loses the ability to run at high speed, but it might pull like a tractor at low speeds. Small overlap prevents exhaust from entering the intake manifold at slow speeds, but can't pull that extra intake charge at high speeds.
As overlap is increased, the engine produces more and more power at high speeds, but it has more and more trouble idling and running smoothly at low speeds. Large overlap can allow exhaust to be pushed backwards into the intake at slow speeds, but serves to charge the cylinders with more fresh air/fuel mixture at high speeds.
So you see, valve timing becomes a balancing act. Something is compromised at one point in order to gain something at another point. The next lesson will get to the meat of the matter, and help you understand the balance.

[perfworks]

/members/perfworks/twolobe.gif
As stated in lesson 2, overlap has a great deal to do with overall engine performance. Small overlap makes low-end torque but less high-end power. Large overlap reduces low-end torque but increases high-end power.
Overlap is determined by two other cam specifications, Duration and Lobe Center Angle.
Duration is the time, measured in crankshaft degrees, that a valve is open. A duration of 204 degrees means that while the valve is open, the crankshaft rotates through 204 degrees.
Duration is measured on two "standards," "advertised duration" and "duration at 0.050"." Advertised duration is measured from when the valve just starts to lift off its seat to when it just touches the seat again. This is measured in different ways by different manufacturers. Some measure when the valve lifter is raised 0.004", some at 0.006", and some at different points yet. So the industry agreed to another standard that was supposed to make it easier to compare cams. In this standard, the duration is measured between the point where the lifter is raised by 0.050", and the point where it is lowered again to 0.050".
The 0.050" standard is great for side-by-side "catalog" comparisons between cams. But if you use engine prediction software on your computer, the software is much more accurate when you can feed it "advertised" duration numbers.
Lobe Center Angle is the distance in degrees between the centers of the lobes on the camshaft.
To increase duration, cam makers grind the lobes wider on the base circle of the cam. This makes the lobes overlap each other more, increasing overlap. More duration = more overlap.
To increase overlap without changing duration, cam makers will grind the lobes closer together, making a smaller lobe center angle. Less lobe center angle = more overlap.
Overlap and duration are the two big factors in cam design. More overlap moves the power band up in the engine's RPM range.
Longer duration keeps the valves open longer, so more air/fuel or exhaust can flow at higher speeds. It works out that increasing the duration of the camshaft by 10 degrees moves the engine's power band up by about 500 rpm.
A smaller lobe separation increases overlap, so a smaller lobe separation angle causes the engine's torque to peak early in the power band. Torque builds rapidly, peaks out, then falls off quickly. More lobe separation causes torque to build more slowly and peak later, but it is spread more evenly over the power band. So a larger lobe separation angle creates a flatter torque curve.
So you can see how a cam maker can tailor the camshaft specs to produce a particular power band in an engine--

Short duration with a wide separation angle might be best for towing, producing a strong, smooth low-end torque curve.
Long duration with a short separation angle might be suited for high-rpm drag racing, with a high-end, sharp torque peak.
Moderate duration with wide separation angle might be best suited for an all-around street performance engine, producing a longer, smoother torque band that can still breathe well at higher RPM.
Remember, there's always a compromise made in this process.

One last item to consider is the lobe centerline. The lobe centerline is the angle of the lobe's center peak, measured in crankshaft degrees when the piston is at Top Dead Center (TDC). In general (but not always), when a cam is installed "straight up," the intake lobe centerline and the lobe separation angle are the same.
The lobe centerline can be altered when the camshaft is installed, by advancing or retarding the camshaft's position in relation to the crankshaft. Advancing the camshaft by 4 degrees will move the power band about 200 RPM lower in the RPM band. Retarding the cam by 4 degrees will likewise move the power band 200 RPM higher in the RPM band. This allows you to fine-tune the engine's performance according to your needs.
But, if you have purchased the cam matched to your needs in the first place, your best choice is usually to install the cam "straight up."

[perfworks]

Once duration, overlap, lobe center angle, and lobe separation angle are determined, the next important cam specification is lift.


Figure 4
/members/perfworks/duration.gif
Figure 4 is a graph that shows both the timing and the lift of an engine's valves for a Comp Cams 270 Magnum camshaft.
The picture is a little grainy, but if you look closely, you can see that this cam has a 110-degree lobe separation angle. The cam is named for its 270-degree advertised duration, shown near the bottom of the graph. The 0.050" duration is 224 degrees. This cam, when installed "straight up," has an intake center angle of 108 degrees, so this one was made with a 2-degree advance built in. It also has just under 1/2 inch of lift.
By these specs (moderate lobe separation angle, moderate duration, 2-degrees built-in advance, and medium lift), this cam is suited for mid to high-end street performance on V8's 350 cubic inches and smaller. Duration and overlap aren't big enough for all-out drag racing, but quite a bit larger than a factory stock cam.
Look at this graph, and you can see the affect of lift. The larger the areas beneath the curves on the graph, the more air/fuel and exhaust the engine can move through the valves. If you make the curves higher by increasing valve lift, you increase how much air/fuel or exhaust the valves can pass.
The affects of lift are pretty straightforward. Up the the limits of the engine's cylinder heads, more lift = more air/fuel/exhaust movement = more power.

There are two ways to increase lift. You can either grind the camshaft with taller lobes, or you can increase the ratio of the engine's rocker arms.
As an example, a small-block Chevy engine uses 1.5:1 rocker arms. What does that mean? I means that if the valve lifter is raised 1 inch, the valve will open by 1-1/2 inches. A ratio of 1.5 to 1. If you replace the stock rocker arms with 1.6:1 or 1.7:1 rocker arms, you open the valve higher with the same camshaft. It's as if you installed a cam with higher lift. Remember, opening the valve higher = more power.
To calculate the affects of increasing rocker arm ratio, use this formula:

Lift with new ratio = Lift with stock ratio X new ratio / old ratio

For example, if your stock valve lift is 0.4" with 1.5:1 rockers, and you want to install 1.6:1 rockers--

New Lift = 0.4" X 1.6 / 1.5
New Lift = 0.427"

There is a limit. Continuing this example, most small-block Chevy engines run best with the valves opening to about 1/2 inch. There are lots of factors involved-- the shape and size of the head's runners, how close the valves are to the sides of the combustion chamber, the size of the valves, etc. The best way to find out the best lift for your engine is to have the heads flow-tested. The flow bench will quickly show what valve lift gives the best flow. Generally, you want to lift the valves just a little bit higher than the opening that gives maximum flow. This is because the valve is at its maximum lift only briefly.

[perfworks]

There is yet one more way to modify valve lift. That is, change how fast the valve opens and closes. This is accomplished by the type of camshaft you use. Each uses its own particular type of lifter.
The first two types, and most common, are the flat-tappet cams, either hydraulic or solid. "Flat-tappet" means that the base of the lifter is flat metal, and it slides on a film of oil (hopefully) directly on the face of the camshaft lobes.


Figure 5

/members/perfworks/hydsolroll.gif



Figure 6, Lifter types

/members/perfworks/lifters.jpg
Hydraulic flat-tappet camshafts are the most common type of cam used in production vehicles, and in most performance engines. Hydraulic flat-tappet lifters incorporate a self-adjusting mechanism that maintains zero lash in the valve train. Zero lash means there is no gap between the parts in the valve train. The lifters, pushrods, rocker arms, and valves are maintained in continuous contact with each other, using oil pressure to make automatic adjustments for heat expansion of the parts. This type of cam, when installed correctly, with the proper oil, and broken in according to the manufacturer's instructions, provides quiet, trouble-free operation. Life expectancy of the cam is equal to the that of the engine as a whole.
There are a few drawbacks to hydraulic lifters. When the engine is operated above recommended speed ranges, to the point where the valves "float," the lifters attempt to self-adjust themselves out of the proper lash setting. Basically, the lifter mechanism over-fills itself with oil, and it "pumps up." This will not allow the valves to fully close, and performance will fall off until the engine speed is reduced and the lifters readjust.
Flat-tappet hydraulic lifters require a camshaft profile that opens the valves relatively slowly in order to prevent "float." Because of the mechanism inside, hydraulic lifters are relatively heavy. Their larger mass causes them to float more easily than solid lifters, so the camshaft is ground with less aggressive lobe profiles. This serves to reduce the area under those curves in the graph you looked at earlier. See the red lines in figure 5. (Note in Figure 5 that the total lift and the duration both remain the same, yet the area under each curve is different.)
Solid flat-tappet camshafts use lifters that do not have the self-adjusting mechanism of hydraulic lifters. They are, therefore, lighter. For performance engines, the advantages of solid lifters over hydraulic lifters should be apparent. Since they are lighter, the engine can rev faster, and the camshaft can be more aggressive, because with less mass the lifters are less prone to "float." When they do float, they don't have a mechanism that will pump up, so the engine will not stumble or misfire, but keep running. All else being equal, solid camshafts allow the use of lighter valve springs, which translates to more power output to the crankshaft (less power used to push the valve springs down, and to slide the lifters on the cam lobes). Solid cams also tend to give the engine smoother idle and higher vacuum.
The downside of solid camshafts is that you must manually adjust the valve lash, and make it part of a regular adjustment schedule. There must be some clearance allowed between parts of the valve train. Insufficient clearance will cause the valves to remain open slightly, once the parts get hot and expand.
Also, many engines are not designed to accommodate manual valve adjustment, and conversion to a solid cam can be costly.
Finally, because of the lash adjustment, solid cams and valve trains make more noise. Some computerized engines with knock sensors simply can not use solid cams.
Which brings us to roller cams.
Roller camshafts camshafts are so named because the lifters they use have ball-bearing-mounted roller wheels on their bases. The lifter rolls on the camshaft, rather than sliding like flat tappet lifters.
The rollers on the bottoms of the lifters allow the cam to be ground with a much more aggressive ramp profile, even over solid flat-tappet cams. The valves can be opened much more quickly, allowing them to spend much more time in their maximum open position.


Aftermarket roller lifters,
showing two different types
of guide bars that prevent
rotation of the lifter
Roller lifters are heavier than flat-tappet lifters, requiring the use of heavier valve springs. But their roller bases eliminate friction on the camshaft. The power increase from friction reduction easily overcomes the power lost to heavier springs. So the valve springs used can be even heavier yet, allowing higher engine speeds.
With their more aggressive lobe profiles, roller cams have great advantages over flat-tappet cams. Compared to a flat cam of the same duration, a roller cam has the same low-end torque and idle. But its high-end performance is like a cam of much longer duration. For street engines, a roller cam can give smooth idle and great gas mileage, yet perform like a strip cam. For race engines, roller cams can push performance higher where flat-tappet cams have reached their limits.
Because the lifters roll on the face of the camshaft, rather than slide, you can replace the camshaft without replacing the lifters. Being able to re-use the lifters on a new camshaft offers a cost advantage.
However, cost is also the main downside of roller camshafts. Roller cams are expensive. Roller lifters are expensive. Because of the advantages listed above, roller cams and lifters must be made of higher quality materials. Converting a flat-cam engine to a roller cam requires the purchase of not only the cam and lifters, but also heavier springs, and often stronger pushrods and rocker arms.
As for the lifters, they can not be allowed to rotate in their bores. The roller must be kept square to the camshaft. Factory roller lifters have square-machined bosses on top that fit into a guide plate mounted on the top of the engine block. Or they have a pin in the side that engages a groove machined into the lifter bore on the block. Aftermarket lifters uses guide bars that tie the lifters together in pairs, to prevent rotation. Converting a flat-cam engine to a roller cam requires machining the block to accept the lifter guide plate, cutting guide grooves in the lifter bores of the block, or using the even heavier and taller aftermarket lifters (with matching, short pushrods).
Failure to install heavier springs and stronger parts can result in valve train destruction at high engine speeds.
Roller cams come in both hydraulic and solid types, with the same advantages and disadvantages of their flat-tappet cousins.

[perfworks]

Camshaft Selection
Camshaft selection often seems like voodoo or art. But it really is a science. All you have to do is know the basics, and cam selection is greatly simplified.

Let's review the basics--
Duration, Lobe Separation Angle, Intake and Exhaust Centerlines, and Overlap are all determined by four basic cam specs: Intake Valve Open ( IVO), Intake Valve Close ( IVC), Exhaust Valve Open ( EVO), and Exhaust Valve Close ( EVC).
These "valve events" are measured in crankshaft degrees Before or After Top Dead Center (BTDC or ATDC) and crankshaft degrees Before or After Bottom Dead Center (BBDC or ABDC).
These are confusing to most people, and make cam comparison difficult. Fortunately, we can use Duration and Separation Angle to compare cams.
Comparison of Crane #2030 to a cam with 20 degrees
shorter duration (lines with the blue markers). See
how 20 degrees less duration moves the torque peak
(green lines) down in the rpm range by 1000 rpm.
Notice also how both peak horsepower (red lines)
and peak torque drop.

Duration--
Duration is the number of degrees of crankshaft rotation that a valve is open. In this case, look at the "Advertised Duration." Crane "advertises" that the intake valve will be open while the crankshaft rotates 260 degrees, and the exhaust valve will be open while the crankshaft rotates 270 degrees.
Duration determines the Basic RPM Range where the engine will produce the most torque (the so-called "power band").
Duration is specified by two "standards." Duration at 0.050" is valuable for comparing camshafts in the catalogs. Advertised duration is valuable for use in computer engine simulation programs, like Motion Software's Dyno 2000. The longer the duration, the higher the power band moves in the RPM range. For each ten degree change in the duration (measured at .050” lift, not "advertised" duration), the power band moves up or down in RPM range by approximately 500 RPM.

Duration @ 0.050"--
This is simply a standard that has been established to help you compare cams. The cam makers agreed to take measurements at the points where the lifter is raised 0.050" above its resting point. This was done because there is no good way to standardize "advertised" duration, which is supposedly when the lifter just begins to move.
Power prediction software, like Dyno2000, can estimate advertised duration from 0.050" specs, but their best accuracy is realized when using "advertised" numbers.

Here's another comparison you can make. Subtract the 0.050" duration from the advertised duration. This difference can give you an idea of the aggressiveness of the cam's grind. The smaller the difference, the faster the valves are being opened, and the more power the cam will make.

Lobe Separation Angle determines where in the power band the torque peak will occur. A short separation angle (below 108 degrees) makes the torque build quickly, peak early in the power band, then fall off quickly. Short separation angles produce a "peaky" torque curve. A long separation angle (above 112 degrees) makes the torque build gradually, peak later, and drop off more slowly. Long separation angles produce a "flat" torque curve.


Affects of Lobe Separation. Compare the #2030 cam at 116 degrees
lobe separation with one having a 106-degree separation (lines with
markers). Look particularly at the the red horsepower lines. The shorter
lobe separation angle produces more peak horsepower, but with a loss
of low-end torque. Shorter lobe separation angle is better for a drag
engine than a street machine, due to an increase in valve overlap.
Intake Centerline Angle fine-tunes the position of the power band. Advancing the centerline 4 degrees will move the torque peak about 200 RPM lower in the power band. You can do this by advancing the cam upon installation, or it may be ground into the cam by the manufacturer.
Overlap is determined by Duration and Lobe Separation Angle, which are more important to think about. Long overlap moves the power band up in the RPM range, makes for a peaky torque curve, and produces a rough idle. Long overlap comes from long duration and short separation angles. See the relationship? Short overlap improves idle, moves the power band down in the RPM range, and produces a flatter torque curve. Short overlap comes from short duration and long separation angles.
Lift greatly affects the engine's maximum torque, but mostly in high RPM applications. Lift has little affect on a low-RPM towing engine, where low-end torque is most desirable. Lift that is too small will prevent a street performance or race engine from making its best torque. In these applications, increased lift is desired up to the limits of the heads' flow characteristics and mechanical interference. Lift is adjusted either by grinding the camshaft lobes to a particular height, or by changing the ratios of the engine's rocker arms.
"Advertised" Duration
Advertised duration has fallen somewhat into disfavor in the the camshaft world, but don't discount it just yet.
The reason the industry agreed on 0.050" specs is because they couldn't agree on some other standard. Some cam makers, like Crane, list their advertised numbers at 0.004" of valve lift. Others, like Competition Cams, lists their advertised numbers at 0.006" of valve lift. Still others follow some other standard. Because of this, it can be difficult to compare camshafts between manufacturers.


Affects of Lift-- Compare the #2030 with a cam of 0.200"
less lift (lines with markers). Notice how the torque (green
lines) starts out equal at lower rpm, but the overall torque
and horsepower are hurt by less lift, a sure sign of an
engine that isn't getting enough mixture at higher rpm.
However, I like to have the advertised numbers for two reasons.
First, if you're using software like Dyno2000, the software tends to run faster and be more accurate when using advertised duration numbers. This is because the software simulates intake and exhaust flow even at low valve lift. If you give it 0.050" numbers, the software estimates the advertised duration of the cam.
Second, I like to compare cams by subtracting the 0.050" duration from the advertised duration, and then looking at the lift. Here's an example, comparing two "similar" cams from two different makers..

While these are VERY similar cams in 0.050" duration, notice the differences between them.
First, compare separation angle. The Comp probably has a stronger torque peak at a higher RPM range. The Comp's similar duration with smaller lobe separation equals more overlap, which moves the torque peak higher in the RPM range and peaks more sharply.
If you compare advertised specs, the Crane would appear to be the slightly hotter cam. But Crane measures at 0.004" and Comp at 0.006". Extend the Comp's duration a degree or two to make up for that, and the two cams would appear to be the same intake duration, the Crane slightly longer on exhaust. So the Crane cam would get the nod for smoothest and strongest power output.
But compare the 0.050" specs, and the Comp looks like the hotter cam. Intake duration generally has more effect on power output than exhaust duration. So in 0.050" specs, the Comp has the edge in power output.

Camshaft comparison
Cam Advertised @ lift 0.050" Difference Lobe Separation Lift
Crane 104221 roller 260/270 @ 0.004" 204/214 56/56 116 0.429"/0.452"
Comp 08-408-8 roller 258/264 @ 0.006" 206/212 52/52 110 0.480"/0.487"

So how do you know? Subtract 0.050" duration from advertised duration, and get the rest of the story.
We'll assume 1.5:1 rocker arms. With the Crane cam, the valve will lift the valve from 0.004" to 0.075" (0.050" spec is measured at the lifter, remember) and back down to 0.004" within 56 degrees of crankshaft rotation. The Comp will raise the valve from 0.006" to 0.075" and back to 0.006" within only 52 degrees of rotation. Even if you add a degree or two to the Comp's advertised numbers, it still opens and closes the valves faster.
Notice also that the Comp cam has higher lift, even though the duration numbers are similar between the cams.
The differences between the advertised and 0.050" specs say that the Comp is opening and closing the valves faster. The Comp cam's higher lift with similar 0.050" duration says the Comp is opening and closing the valves faster. This indicates that there is a significant difference between the two cams. The Comp cam opens the valves considerably quicker than the Crane does, and probably holds them wide open longer. That means more flow per revolution of the engine.
So in this comparison, the Comp is probably a significantly hotter cam at wide open throttle, because it can flow more air/fuel and exhaust (duration difference and lift). It will have a sharper torque peak at a higher RPM range and produce more peak horsepower (due to shorter lobe separation angle compared to duration).
The Crane will deliver a smoother power band over a wider RPM range (longer separation angle), and probably accelerate from low RPM more quickly (less overlap for more bottom-end torque).
At idle, you won't be able to tell the difference.

Which is better? Depends. If I were choosing between these cams for an engine below about 325 cubic inches, I'd opt for the Comp to get a little more oomph up top. For an engine over 325 cubic inches, I'd take the Crane to maximize the larger engine's torque band and enhance streetability.
You can't use this as a "one brand is better than another" argument. You've got to look at the cams, study up, do your homework. And above all, talk to the cam makers' technicians before you buy.

How much Lift?
That depends on your heads' flow characteristics. To choose the right camshaft, you really need to know how your cylinders heads flow. You see, cylinder heads don't flow more and more air as you lift the valve higher and higher. Airflow through a head reaches a peak as the valve is opened, then starts to drop off as the valve is lifted beyond that peak.
The general rule of thumb for lift selection is to lift the valve 20-25% past its peak flow point. So if your head flows best at 0.4" of lift, use a cam/rocker combination that will lift the valves between 0.480" and 0.500". (20% of 0.4" is 0.08". 25% of 0.4" is 0.1". Add 0.08" or 0.1" to 0.4" to get your best total lift.) The reason for this is, if you lift the valve only to its best flow point, then the valve only flows best when it's wide open, which really isn't that long a time. Instead, you want to lift the valve PAST its peak. This way, the valve passes through its best flow area twice. The net result is more total flow during the open/close cycle of the valve. But you don't want to raise it too much past that point, or you lose total flow by going too high. 20%-25% past peak seems to give the best result.
The main thing you need to know here is-- At what valve lift do your heads flow the best? If your heads flow their best at 0.35" of lift, then a 0.500" lift cam won't gain you anything over a 0.440" lift cam.

Cam Specifications, Crane PowerMax 2030, Part number 104221
Degrees
Duration @ .050 Int./Exh. Degrees
Adv. Duration
Int./Exh. Degree Lobe
Separation Open/Close
@ 0.050" Cam
Lift Int./Exh. Lash Hot
Int./Exh. Gross Lift
Int./Exh.
204
214 260
270 116 (14) 38
43 9 .000
.000 .429
.452

Open/Close and Lash (See table above)--
These are the actual open and close measurements for the cam, and the valve lash adjustment. The numbers can be confusing, as I've proven myself right here. (I had to make corrections on this page, thanks to an alert reader.)
Valve Open/Close events are listed in crankshaft degrees, and you have to be careful when you read them. Pay attention to this--
Intake valve "Open" is listed as Before Top Dead Center (BTDC), but intake valve "Close" is After Bottom Dead Center (ABDC).
Exhaust valve "Open" is Before Bottom Dead Center (BBDC) and exhaust valve "Close" is After Top Dead Center (ATDC).

How can you remember if these events are "before" or "after" without having to look it up? The valve "Opens Before" it closes. Or, the valve "Closes After" it opens.
The intake stroke moves the piston from top to bottom, so the intake opens near Top and closes near Bottom.
Likewise, the exhaust stroke moves the piston from bottom to top, to the exhaust valve opens near bottom and closes near top.
So, remembering the little memory helper and knowing the 4-stroke cycle, you can remember that Intake numbers are Open BTDC and Close ABDC; and exhaust numbers are BBDC and ATDC.

Simple, right?

Now, to muddy it up a bit, a number in parentheses ( ) is a negative number, and is therefore opposite the rule. So in the table above, notice that the intake valve "open" is listed as (14). So, since intake "Open" is "Before" and it's near Top Dead Center, this means 14 degrees "After" Top Dead Center.

Again, these numbers are given in 0.050" specs, and are more for comparison than for actual prediction. The actual shapes of the lobes make big differences in performance, even between cams of the same "on paper" specs.

The Crane 2030 Roller cam (table above) will push the intake lifter up 0.050" when the crankshaft is at 14 degrees After Top Dead Center (ATDC), and it will lower it to 0.050" when the crankshaft is at 38 degrees After Bottom Dead Center (ABDC).
Likewise, the exhaust valve will be pushed up to 0.050" at 43 degrees Before Bottom Dead Center (BBDC), and lowered to 0.050" at 9 degrees ATDC (After Top Dead Center).

Lash adjustments for this cam are listed as 0.000" for both intake and exhaust.. "Lash" is how much space is required between the end of the rocker arm and the top of the valve stem when the engine is fully warmed up.
A last specification of 0.000" means that the cam is made for hydraulic lifters. A solid-lifter cam will have adjustment specs of greater than 0.000".
Roller Camshaft "Magic"
A roller camshaft should have steeper lobe flanks, or ramps, in comparison with a flat-tappet cam of similar grind. Above, I outlined how to "see" how steep a camshaft's ramps are. Simply calculate the "Duration Difference" of the cam-- subtract the 0.050" duration from the advertised duration. The smaller the difference between the two, the steeper the lobe ramps are. The steeper the lobe ramps, the faster the valve is opened and closed, and the longer the valve is at its maximum open position.
Also compare lift in relation to the duration difference. Higher lift combined with a shorter duration difference equals a more radical grind.
Is that roller cam a true roller profile, or is it just a re-ground flat-tappet cam? Compare its duration difference to that of a flat-tappet cam with the same 0.050" specs. The difference, if any, will be apparent.

[perfworks]

Practical Camshaft Selection
Now that you can look at a camshaft's basic specification in a catalog, and make comparisons on your own, you can now use the tools that the camshaft makers give you.
The cam makers' catalogs contain information valuable for helping you make a decision on a camshaft. Let me state right now that I do not believe there is any difference in quality and workmanship between the major camshaft manufacturers. In fact, many factory cams are not made by the car makers, but are made by the aftermarket cam companies for the car makers. Choose your cam based on what your goals are and what your budget will support, not on brand name.

What type of cam? Flat or Roller?
Use a Flat-Tappet Cam--
Anytime a flat tappet cam will do the job, which is most of the time.
Use a Roller Cam--
When engine stress levels are high
When competition requires valve opening and closing velocities faster than a flat-tappet can provide
When you simply must have that extra level of performance, but can't sacrifice emissions or low-end drivability
When you are replacing an existing roller camshaft, and you don't want to lose performance.

The camshaft makers' catalogs provide all the information you need to select a camshaft. In the example below, you will learn what to look for, and how to read the catalog. Of course you're going to look for duration, lift, and separation angle. But there are other factors to consider, the most important being that the cam maker certainly knows more about all of this than you do. Once you have chosen several candidate cams for your car, then you can use what you have learned in the previous lessons to make your final decision.
The example used is a Crane Cams #104221 in their 2030 grind profile. (Example only. Not an endorsement.) Crane's catalog is VERY complete in the information it gives. Other makers may present you with little more than a table or chart. But the info you need is there. You just have to look for it.

Direct from the Crane catalog--

Chevrolet V-8, 87-98
87-92 305 (5.0L)-350 (5.7L) cu. in. hydraulic roller

Application Series & Grind Number Cam Part Number & Emissions Code Lifters Part Number
Builds mid and upper RPM performance in 87 TPI engines with 5-speed trans. and all rear gear ratios. Also fits 88-89 305 engines w/5-speed and 2.73 or 3.27 rear gears for mid-range performance. Adj. Fuel Pressure Regulator ( 99470-1) recommended for maximum performance. (50 state legal for listed applications, C.A.R.B. E.O. D-225-22) Basic RPM 1500-5000 CompuCam
2030 104221
10530-16

Application. What is the cam made to fit? You can't put a Ford camshaft in a Dodge engine. Or a big block cam in a small block. Won't fit. Wouldn't work if it did fit.
In this example from the Crane catalog--
Chevrolet V-8 87-92
305 (5.0L)-350 (5.7L) cu. in.
This is what the cam fits. It won't work in anything else. Yes, it will slide into most any small-block Chevy, but you'll have to modify the block. The next example will show you why.
Type of Cam. What type of cam is it? Is it for solid flat tappet lifters? Hydraulic flat tappet lifters? Hydraulic roller lifters? Solid roller lifters? Mushroom tappet lifters?
In this example from the Crane catalog--
87-92 305 (5.0L)-350 (5.7L) cu. in. hydraulic roller
You can't mix and match camshaft types and lifter types. If you intend to put this camshaft in something other than an 87-92 305/350 roller block, you'll have to have the block machined to take the roller lifters, or use special, expensive aftermarket roller lifters with guide bars.
Basic RPM. What RPM range is the camshaft designed to operate in? Closely tied to this is your application's 60 MPH Cruise RPM.
It is important to be sure the vehicle’s drive train is capable of matching your selection. The cruise RPM at 60 MPH is a way of rating your rear end gearing and tire diameter to determine if these components match the RPM potential you are desiring.
60 MPH Cruise RPM is easy to determine. Drive 60 mph in your car's 1:1 drive gear (3rd gear with a 3-speed; 4th gear with a 4-, 5-, or 6-speed) and read the engine speed off the tachometer. If you don't have a tach, hook up a test tach to the engine, string it inside the car, and go for a drive.
You want your 60 MPH Cruise RPM to be well inside the Basic RPM range of the camshaft. Otherwise you won't get the results you want.
In this example from the Crane catalog--
Basic RPM 1500-5000
Cam Description. Some catalogs tell you more than others do. But they all have some kind of description of what the camshaft is for.
The cam must be matched to your engine's compression ratio. Too little compression ratio (or too much duration) will cause the cylinder pressure to drop. This will lower the power output of the engine. With too much compression ratio (or too little duration) the cylinder pressure will be too high, causing pre-ignition and detonation. This condition could severely damage engine components.
The cam must be matched to your vehicle's rear-end gear ratio. Long duration cams require lower (numerically higher) rear end gears. This is because long duration equals less low-end torque. High gears with a long duration cam will give poor drivability on the street, or a poor launch off the line.
Example from the Crane catalog--
Builds mid and upper RPM performance in 87 TPI engines with 5-speed trans. and all rear gear ratios. Also fits 88-89 305 engines w/5-speed and 2.73 or 3.27 rear gears for mid-range performance. Adjustable Fuel Pressure Regulator recommended for maximum performance.
Pay attention to this. This cam is not well suited for a 383 with 4.11 rear gears. A 383 with this cam will likely have very poor top-end performance as it runs out of air. It's also too much cam for a 283, unless you're going with very high gears or a very light car.. And it won't pull well in a car with 2.67 rear gears. It will be OK in a 305 or 350 with 3.55 gears or lower (numerically higher), but with a lower rear end, a more radical cam than this one will make you happier.
Emissions. If this is a street machine, and you live in an area with emissions tests, you can't afford the time and money to install a camshaft that guarantees an emissions test failure.
If you have to meet emissions, look for a CARB exemption number. (CARB stands for "California Air Resources Board," and they pretty much determine what is emissions legal and what is not, since California has the stiffest emissions laws.). Many cam listings also display a number in a diamond symbol. A "1" symbol means "50-state legal" and carries a CARB number. A "2" symbol means the part doesn't have a CARB number, but it is expected that it will pass emissions tests in all 50 US states. A "3" symbol means it will not pass emissions tests-- period.
Example from the Crane catalog--
(50 state legal for listed applications, C.A.R.B. E.O. D-225-22)
Notice it says "for listed applications." The emissions may be no good if used in a different application or setup.
Finally, look at the specs--
Degrees Duration @ .050 Int./Exh. Degrees Advertised Duration Int./Exh. Degree Lobe Separation Open/Close @.050" Cam Lift Int./Exh. Lash Hot Int./Exh. Gross Lift Int./Exh.
204
214 260
270 116 (14) 38
43 9 .000
.000 .429
.452

These specs will allow you to make comparisons between this cam and others, to make the final decision as to what cam to buy.
Notice you get both 0.050" and advertised duration numbers. This lets you compare the "duration difference" between similar cams, to get an idea of the aggressiveness of the ramps.
Recommended components. Last of all, most manufacturers also list their parts numbers for lifters, rocker arms, push rods, etc., that will work best with the cam you're looking at. It is not necessary to buy those particular parts, but comparison to what you have is important. By looking up the manufacturer's recommended parts, you can compare spring weights and rocker ratios from cam to cam. Some of this information is on the camshafts Spec Card. See the next lesson.
Grind pattern. Notice in the specs table above that the example camshaft has longer duration on the exhaust than it has on the intake. This is done to make up for the fact the exhaust valves and ports are always smaller than intake valves and ports. The longer exhaust duration also enhances the scavenging affect, that is, the tendency to draw more intake charge into the cylinder by using the vacuum created by the exiting exhaust.
This is called a "dual-pattern" cam grind. (In a "single-pattern" cam, the intake and exhaust lobes are ground identically.) The longer exhaust duration raises the power band slightly and flattens the torque curve.
If you have any specific questions, put in a call to the cam maker. The best ones have telephone, email, or online technicians who are happy to answer your questions and make specific recommendations.

Very Generalized Camshaft Characteristics
Keep in mind that these are gross generalizations. Follow the guidelines above and consult with the camshaft maker for your specific applications.
Duration Separation
Angle Result
Short Short Strong, narrow, low-end power band. Useable from idle to 3500 rpm or so. A dump truck engine or heavy off-road vehicle.
Short Long Wide, low-end power band. Useable on the highway up to 4000 RPM, especially with exhaust headers, but no high-RPM pull. Good for towing heavy trailers down the interstate.
Moderate Short Mid-range power peak. Power band from idle to 4000. Gives a power peak near the top of the power band that might help pulling a 5th wheel up mountain grades.
Moderate Long Wide, extended power band, with peak between 3500 and 5000 rpm. Useable from off-idle to 6500 rpm with accompanying head, exhaust, and intake mods. Great choice for a daily driver street fighter machine.
Long Short Narrow high-end power band, up to 11,000 rpm or more. Peaky torque that works best in an all-out drag race engine with close-ratio transmission and low rear-end gears.
Long Long Wide, high-end power power band. Pro-street drag engine. Street machine with no power brakes and manual heater controls, and a rough idle.

[perfworks]

How to Read a Cam Card
Finally, you can get the camshaft's spec card, before you buy it. Many manufacturer's website allow you to download the card directly. Others will mail you the card for any of their cams. All you have to do is call and ask for it.
Here is the Cam Card for the example of the previous lesson, the Crane 2030 roller cam--

Part Number: 104221
Grind Number: COMPUCAM 2030 HYD. ROLLER SPECIAL
Engine Ident: 1987-1989 CHEVROLET V-8 305 CU.IN.



VALVE SETTING: INTAKE .000 EXHAUST .000 ----> HOT

LIFT: INTAKE @CAM 286 @VALVE 429 ROCKER ARM RATIO
EXHAUST @CAM 301 @VALVE 452 1.50
ALL LIFTS ARE BASED ON ZERO LASH AND THEORETICAL ROCKER ARM RATIOS

CAM TIMING OPENS CLOSES ADV DURATION
@ --- INTAKE --- --- 260 °
-- LIFT EXHAUST --- --- 270 °

SPRING REQUIREMENTS
TRIPLE DUAL OUTER INNER
PART NUMBER 99848

LOADS:
CLOSED 105 LBS @ 1.700 OR 1 45/64
OPEN 265 LBS @ 1.280
RECOMMENDED RPM
RANGE WITH MATCHING COMPONENTS
MINIMUM RPM 1500
MAXIMUM RPM 5000
VALVE FLOAT 6500

CAM TIMING OPENS CLOSES MAX LIFT DURATION
@ .050 INTAKE (14)ATDC 38 ABDC 116 °ATDC 204 °
TAPPET LIFT EXHAUST 43 BBDC (9)BTDC 116 °BTDC 214 °

REMARKS:
AN ADJUSTABLE FUEL PRESSURE REGULATOR ( CRANE
P/N 99470-1 ) IS REQUIRED FOR USE WITH THIS
CAMSHAFT.




As you look down through the Spec Card, you can see all the adjustments and specifications for the cam.

The first three lines tell you the Manufacturer's part number, the grind family, and the engine group it is made for. In this case, it is a Crane #104221 CompuCam, Grind family 2030, and it's an Hydraulic Roller Cam, special. "Special" in this case means its made for 1986 and later small blocks that came with a roller cam from the factory.

The next line tells you how to adjust the valves. This is an hydraulic cam, so the specs are 0.000" lash. A solid lifter cam will have some adjustment other than 0.000". "HOT" indicates that adjustments are to be made on a fully-warmed-up engine.

Next are the lift specs. The first column (@ CAM) is the "raw" lift of the cam. This is the actual height of the cam lobes in thousandths of an inch, and tell you how high the LIFTERS will be raised by the lobes. The second column (@ VALVE) is how high, in thousandths of an inch, the valve will be opened with the specified ROCKER ARM RATIO. The specified 1.50:1 Rocker Arm Ratio tells you what rocker arm the maker is using for calculations. This is NOT saying that you MUST use 1.50:1 rocker arms. It is given to you for calculation purposes only. If you can not use a higher-ratio rocker arm, the cam description (from the manufacturer's catalog) will tell you so. The line that says, "ALL LIFTS ARE BASED ON..." is just clarification. In other words, they are telling you beyond a doubt that the numbers in the @VALVE column are the @CAM numbers multiplied by the ROCKER ARM RATIO.

The first CAM TIMING section is telling you the "advertised" opening and closing specifications for the valves. On the left side you see "@" and "LIFT." The cam maker may put something like "@ 0.004" LIFT" in this section, just for further clarification. In general, if this is blank, the manufacturer is using 0.004" lift as the measuring point for the advertised duration.

The SPRING REQUIREMENTS section tells you all about the valve springs you need to use with this cam. It may tell you if you need single, dual, or triple springs. For this cam, it doesn't matter. But, as is often the case, Crane gives you their own part number for the springs they recommend ("PART NUMBER 99848"). If you don't use their springs, the "LOADS" section tells you that the springs you choose should measure 1.700 inches long when you put 105 pounds of pressure on them. And they should be 1.280 inches long under 265 pounds of pressure. The box on the right tells you that when you use the specified springs, this cam will run best between 1500 and 5000 rpm, and it will let the engine rev to a maximum of 6500 rpm before the valves are prone to "float" (the "VALVE FLOAT" number).

The "VALVE FLOAT' number is based on the recommended lifter type, too. In this example, Crane is assuming that you are using factory-type roller lifters. Remember in the previous lesson, Crane says this cam is for replacement of a "factory roller cam." Therefore you are probably re-using the factory roller lifters. If you are using aftermarket guide bar type roller lifters, which are heavier, you'll probably need heavier springs to get the same valve float limit. Get it? Call the manufacturer for specifics. Or spend extra money for a rev kit.
Heavier springs will not change the power band of the cam, but will raise the "VALVE FLOAT" number. Remember that heavier springs increase valve train stress and rob engine torque (it takes power to push them down).
You could use lighter springs if you're planning to use a rev limiter to match, and gain a little more output torque from the engine. But the manufacturer knows best when recommending spring rates. Spring rates are based on the cam's power band and operating range. With Crane's recommended springs, this engine will give you a usable 6000 rpm redline without valve float. A perfect rpm range for a street engine.

The second CAM TIMING section gives the cam timing specs for comparison to other cams, reported as '@ 0.050" TAPPET LIFT" (not valve lift). The MAX LIFT column tells you the intake and exhaust lobe centerlines in camshaft degrees. To get the Lobe Separation Angle, average the two numbers. In this case, both intake and exhaust center angles (MAX LIFT) are 116, so the average is 116, the lobe separation angle in crankshaft degrees.

Finally, the REMARKS section tells you more that the cam grinder wants you to know. In this case, Crane is saying that in a TPI engine (Tuned Port Injection), you MUST use an adjustable fuel pressure regulator to get the most potential from this cam. Basically, all this means is that to get the best power with this camshaft, you'll need to make some fuel pressure adjustments. They even give you a Crane part number for a pressure regulator that will do the job.
For a TBI (Throttle Body Injection) engine, this also applies. You MUST use an adjustable fuel pressure regulator if you want to get the power. But for TBI the recommended part number won't work, because TPI and TBI injectors operate at different fuel pressures. Even if you did push TBI pressures higher (30 psi is where GM TBI injectors start leaking), you still could not use this part number, because it simply won't fit the car.
For carbureted engines, this is telling you that you MUST readjust your fuel mixtures (by changing your carburetor's jets) after installing this cam. Otherwise you'll be very disappointed. A quality fuel pressure regulator and high-output fuel pump would be a very good idea, too.

[perfworks]

I'll post some pics when i get home .
I have to upload them so they are more visable for each quote.
I know its overkill but it is good for people to know what they are talking about when trying to upgrade the internals of their engine

[PaulMP3]

wow.. i got some reading to do tonight.. nice psot perf..

I wanted to do some custom cams and cam gear.. would it be worth doing on my car with no head work.. Wagner said he has a place that will grind them for me. Nothing to agressive.

[perfworks]

Originally posted by paulmp3
wow.. i got some reading to do tonight.. nice psot perf..

I wanted to do some custom cams and cam gear.. would it be worth doing on my car with no head work.. Wagner said he has a place that will grind them for me. Nothing to agressive.
This is only like half of a percent of the stuff that i had read and still read when i was in school.
I must have shit on disk that can fill this whole forum.
But yes a better and more agressive cam shaft will yield greater responce and a "tuned" power band.
I dont know if Andys guy is the same as mine. Might be.
Im sure we will talk about it next time im up.
Youshould definatly do it.
I have a couple sets of stock cams laying around if you dont want to have any down time to your car.
Just let me know.

[shinzen]

Great info guys- taking some of the "black arts" away from cams and tuning them....

[PaulMP3]

Originally posted by perfworks
This is only like half of a percent of the stuff that i had read and still read when i was in school.
I must have shit on disk that can fill this whole forum.
But yes a better and more agressive cam shaft will yield greater responce and a "tuned" power band.
I dont know if Andys guy is the same as mine. Might be.
Im sure we will talk about it next time im up.
Youshould definatly do it.
I have a couple sets of stock cams laying around if you dont want to have any down time to your car.
Just let me know.

cool... Andy an I talked about possibly making this a winter project... Im gonna wait till after he gets the dyno up and running so we can dyno tune it. Would stock cams work.. I was planning on buying a set of blank cams from protege5online.com.

[mrpopnfresh]

I have the 2 deg advance intake and 2 deg retart exhaust setup right now and my car idles crazy. It sounds like a small V8 or something.

[perfworks]

Originally posted by paulmp3
cool... Andy an I talked about possibly making this a winter project... Im gonna wait till after he gets the dyno up and running so we can dyno tune it. Would stock cams work.. I was planning on buying a set of blank cams from protege5online.com.
Some opinions on the matter vary
IMHO regrinds do the job very well. So your stock cams will work.

[Installshield 2]

holy shit Nick...great info...

I didn't get a chance to finish it all...but I will add a little information pertaining to the FS-DE...

The FS-DE has a relativley high stroke and a relatively low rod ratio...Because of this it will behave very twitchy with cam specs and adjustments...small changes to cam timing can have very large affects...

the condition occurs mostly due to how high the piston speeds are in relation to crank revs...at 6500 rpm the FS-DE's pistons are traveling up and down much faster than say a Honda F20 at the same RPM...despite having the same crank speed...

So with this overlap is a common problem...Engine's such as the FS-DE tend to prefer very small amounts of overlap overall...There is a very short period of piston dwell time at both BDC and TDC, in which too long of overlap will always have adverse affects...(overlap occurs at the exhuast stroke to intake stroke transition, so at TDC of this transition the pistons have a low dwell time...just pointing out at what time this applys...)

With short dwell time there is not enough time in which the piston is "dwelling" or not moving when the crankshaft is still moving...This dwell time allows the vacuum of exhuast to pull in fresh air and fuel while all 4 valves are open...also known as "scavenging", it works best with lower stroke higher rod ratio engines that have longer periods of dwell time...

Also our engine will run fine with virtually no overlap at lower speeds...a very few degrees of overlap would probably be optimum for higher rpm breathing, but too much and you quickly "bleed off" compression...

[Installshield 2]

So Andy...

We may have an issue...If you indeed do need to retard the exhuast cam a few degrees...there will be no way to close off you overlap...being that you will probably still need to advance the intake cam...both on their own will increase overlap, and if done together will double itself (meaning 3 degrees exh retard + 3 deg Int advance=6 degrees more overlap)...If you already have 8 degrees of overlap that may not help at all...

[twilightprotege]

this is really strange to me. the overlap issue that is.

when i think about it, advancing a cam means it opens sooner and closes sooner too. so advancing the intake cam will open it sooner and close it sooner. that alone will decrease overlap. the opposite is for the exhaust cam.

i change the initial post just now...is that better?

[thewrench]

Edit: Post deleted because I'm a dumbass, and was probably causing more problems than helping. :)

JT

[twilightprotege]

JT have you got your cam gears yet?

so what you're saying is that my initial post is now correct in terms of what advancing and retarding on the cam gears does?

[thewrench]

I think the post of yours before mine is correct, no matter what the first one says. :) I'll go back and look again. Hit reload, I edited my pic to be a little more explanatory.

JT

[thewrench]

And no, I haven't gotten mine yet. I DO think your initial post is correct, at least as to the effect on the overlap, as for the performance effects, I guess we'll find that out later. I probably won't install mine until I get some cams, our spring of next year. I'm trying to make sure I've got the parts and the knowledge before I start.

James

[twilightprotege]

cool. yeah i'm really looking forward to playing around with my cam gears when i get them hopefully soon.

i know my engine has a lot of potential. i know the stock exhaust sucks, but that's something i'm going to have to live with for a bit. was thinking of getting basically a dump pipe from the stock header and having it come out just behind the passenger front wheel - for track days only ofcourse.

[perfworks]

As promised the pics are up on the posts. It should help generalize some of the info and get everyone on the same page.

[twilightprotege]

thanks perf - so to work out valve overlap is pretty easy then (according to figure 5)...basically IVO + EVC? so in that picture it's 48 degrees of overlap?????

[perfworks]

Originally posted by twilightprotege
hey...

here's some general info on what i've found about adjusting the cam gears on a DOHC car...

Advancing Intake and Exhaust : In general, this will provide the car with more bottom end power, and will decrease top end. Advancing both cam gears will move overlap earlier but will not increase it.

Retarding Intake and Exhaust : This will increase the cars top end, but will decrease low end. Retarding both cam gears will move the overlap later and but will not change the amount of overlap.

Advance Exhaust Only : This will help the cars top end, and it increases overlap.

Retard Exhaust only : This will help the cars mid range power, very useful for cars with big turbos / big cams. Decreases overlap.

Advance Intake only : This will decrease overlap and helps the cars bottom end and mid range power.

Retard Intake only : This will increase overlap and help top end.

so it looks like to me with my setup as it stands at the moment, i'm going to try advancing the intake cam by 2deg and retarting the exhaust by 2deg.

comments???
Now if you want to double check your original post given the information provided it should get a couple of things straight.

Now to start with your first statement:

Yes if you advance both cams then the torque curve and power band will happen earlier in the cycle. About 100rpms sooner for every 2 degrees of advance.
And again you are right the overlap does not increase or decrease. It will be at the same proportion at the stock setup.

Statement number two is also right on the mark.

Now advancing the exhaust cam. (so that it would make the exhaust valve open sooner.) This DECREASES overlap. In turn helps bottom end but stifles top end breathing.
Next statement.
This is the opposite as stated above. It will INCREASE overlap and generally help top end volumetric efficiency.
Now this generally will also NOT help turbo cars. They require almost NO overlap at all and alot of lift.

Now advancing the intake sprocket will increase overlap and the top end responce.

Now so on and so on. Again dont forget that depending on the AMOUNT of advance or retard, that will tell you if it will help in the low mid range or the top
If you advance your STOCK intake cam 2 degrees and retard the exhaust 2 degrees it will increase overlap and improve the top end breathing ability of the engine. IN THEORY. That is if the stock units arent timed that way already. (i doubt they are) They are basically degreed for emmisions and little overlap.

My two cents
Regards Nick

EDIT i should add that the FS motor DOES not like to rev so i would most likely not get too agressive with overlap. At least not with the stock cams. It may fall off early and make you feel you need more adjustment than you really need.

[perfworks]

Originally posted by twilightprotege
thanks perf - so to work out valve overlap is pretty easy then (according to figure 5)...basically IVO + EVC? so in that picture it's 48 degrees of overlap?????
Measured at specific .050 yes that is correct

[twilightprotege]

so valve overlap is measured at 0.050"?

oh i get the individual advancing and retarding now. i was thinking about it wrong. i was thinking the intake would open then exhaust, when it's actually the other way around. DURRRR!!!!! :doh:

yeah, so advancing the intake increases overlap, retarding reduced overlap.

advancing the exhaust decreases overlap, retarding increases.

maybe we should start a new thread with initial correct info! hehe

[perfworks]

.050 is the standard in which the various cams can be compared to on paper. That way cranes 270 can be matched and compared to crowers 270
They are measuring off the lash on the lifter rather than the valve off the seat.

[perfworks]

now if the intake valve opens earlier and the exhaust valve opens later this increases overlap and i just confused you some more.:D

[twilightprotege]

hehehe...now you can see how my mind was going but, if, what about, but, then...hehehehe

so to clarrify....

intake cam - advancing reduces overlap, retarding increases it.
exhaust cam - advancing increases overlap, retarding decreases it.

right?

so yeah, when i look at my own cams, i have the figures for @0.050", so i'll be able to work out what overlap i have no pretty easy then. cool. i wasnt sure if it was at seat or at 0.050

[perfworks]

Originally posted by twilightprotege
hehehe...now you can see how my mind was going but, if, what about, but, then...hehehehe

so to clarrify....

intake cam - advancing reduces overlap, retarding increases it.
exhaust cam - advancing increases overlap, retarding decreases it.

right?

so yeah, when i look at my own cams, i have the figures for @0.050", so i'll be able to work out what overlap i have no pretty easy then. cool. i wasnt sure if it was at seat or at 0.050
Now i think we got 50% cleared up. MY ORIGINAL post was correct. I was tired and thought i said something backwards.
If you say advance to mean the intake valve will open sooner then:::

Advance will increase overlap so long as the exhaust cam stays stationary. Duration and lift have not changed. And wont unless the actual grind changes.
Retard the intake cam will DECREASE overlap and so on.

Again this is stating that if you mean advance to start the process earlier and so on.:D

[twilightprotege]

yep, that's what i mean by advance...

ok, lets try again. i just keep getting confused because you immediately think ok, intake happens then exhaust, but it's the other way around, the exhaust cam is first (pushing out the gases), then intake (sucking in the air and fuel)

intake - advancing increases overlap. retarding it decreases it
exhaust - advancing reduces overlap, retarding increases it

god this is funny...so much conversation and backflips and changes over a relatively minor thing! hehehe

so this was my original post (un-edited) from http://www.prostreetonline.com/pso/pages/techtips/showarticle.asp?articleid=7

Advancing Intake and Exhaust : This will provide the car with more bottom end power, and will decrease top end. Advancing both cam gears will move overlap earlier but will not increase it.

Retarding Intake and Exhaust : This will increase the cars top end, but will decrease low end. Retarding both cam gears will move the overlap later and but will not change the amount of overlap.

Advance Exhaust Only : This will help the cars top end, and it reduces overlap.

Retard Exhaust only : This will help the cars mid range power, very useful for cars with big turbos / big cams.

Advance Intake only : This will increase overlap and helps the cars bottom end and mid range power.

that sort of sounds strange now...like the one straight above...advancing intake increases overlap and helps bottom end? :wtf:

[thewrench]

Haha, I thought I had a complete handle on this, but now if you look at it from the perspective of the exhaust opening first, then I'm totally back-asswards and my cute little illustration is off. God forbid don't delete any of this any time soon, I'm going to have to take some time to digest it all. It makes sense from that perspective, I just wasn't looking at it that way. I'm also used to dealing with v8s, where unless you're grinding your own cams, you're just looking at overlap as a parameter and it's not adjustable.

James

[perfworks]

Increased overlap will kill bottom end

[perfworks]

Originally posted by thewrench
Haha, I thought I had a complete handle on this, but now if you look at it from the perspective of the exhaust opening first, then I'm totally back-asswards and my cute little illustration is off. God forbid don't delete any of this any time soon, I'm going to have to take some time to digest it all. It makes sense from that perspective, I just wasn't looking at it that way. I'm also used to dealing with v8s, where unless you're grinding your own cams, you're just looking at overlap as a parameter and it's not adjustable.

James
Its not really exhaust happening first. The 4 stroke process is constant.
The intake valve will open "x" amount of crankshaft degrees. Then it will close for compression and power strokes. Right before the power stroke is over the exhaust valve opens and sometimes stays open a little too long. AT THE SAME TIME then the intake is opening again. Thats when you get overlap. Once the intake valve opens.
In some cases this is good. For forced induction vehicles overly aggresive cams that have obscene overlap for top end performance will back fire and "push" the fresh charge right out the exhaust.
The idea is to advance the exhaust timing slightly and increase the lift on both cams. That way duration and overlap are conservative

[thewrench]

OK, I was looking at it as if while the intake is open the exhaust begins to open, but you're (not that I disagree at all) saying that while the exhaust is open the intake opens. In my inaccurate example if the intake opens earlier it would also close earlier therefore decreasing overlap, but in your correct example, if the intake opens earlier it doesn't matter when it closes because the exhaust valve will still be open, therefore it will increase overlap. I think I've got it now. Whew, I wish somebody could get a car on a dyno to see what the results are.

James

[twilightprotege]

yeah that's why i said :wtf: when that dsm page said increased overlap will be better for bottom end...

as soon as i get home tonight i'll post how much overlap my cams have...then we can start to talk about what i should do with my cam gears...

so here's what we've got so far :

<b>advance intake cam only :</b> This will increase valve overlap. Will help with top end power
<b>retard intake cam only :</b> This will decrease valve overlap. Will help with bottom end power
<b>advance exhaust cam only :</b> This will decrease valve overlap. Will help with bottom end power
<b>retard exhaust cam only :</b> This will increase valve overlap. Will help with bottom end power

so from the above, we can assume the following (hopefully)
<b>advance both intake and exhaust cam :</b> This will move the power band down in the rev range. Overlap will not change if degrees over advancement for both cams are the same. This will be apx 100rpm lower for every 2 degrees advancement
<b>retard both intake and exhaust cam :</b> This will move the power hand up in the rev range. Overlap will not change if degrees over advancement for both cams are the same. This will be apx 100rpm higher for every 2 degrees advancement

so this is all correct? everyone agree? i would however like to check the 2 degrees/100rpm statement, but it sounds right

[twilightprotege]

well....here's some interesting information.....got my cam sheet in front of me and...

the cam - overlap @0.050" is 6deg....now when you take into account the clearance between the shim and cam (this is 0.012" rather than my current 0.009")...overlap @ 0.050" is -1deg

i must have mis-heard the cam guy when he told me the overlap

very very interesting indeed.....so what do you all think i should do with my cam gears? perf? install?

[Installshield 2]

Andy here is some more info...

Retarding the exhuast is better for lowend, becuase of the blow down affect...Advancing the exhuast is needed for higher rpm breathing...

So I would say that advancing the exhuast cam only, in a case where is increases the blow down affect, will have no benefits on lowend power...mostly becuase at those crank speeds the pistons are not allowed to take full advantage of each mixture expansion (the exhuast valves vent/begin to open before BDC of the power stroke...

Advancing the intake cam and retarding the exhuast cam together will do very different things on two different DOHC engines...The benefits for high rpm breathing are becuase of an increase in overlap...but overlap in degrees needed for high rpm powerbands are not constant from engine to engine...

Same applys though somewhat with advancing the intake and exhuast cam together...Advancing the intake cam allows better "ram" affects, which are better for high rpm breathing, as well as the advanced exhuast cam ("blow down" is increased)...but this is all relative to the current timing of the cams...But we do know that advancing the intake cam is good for high rpm breathing becuase of the ram affect, and that advancing the exhuast is good for high rpm breathing becuase of the blow down affect...this can only be "in general"...we do not know yet if this applies 100% to an FS...


I am having trouble finding information that doesn't argue with itself online...I have been looking since you started this Andy, to break it down simply...but none of th other places info is adding up completely...

[Installshield 2]

Originally posted by twilightprotege
well....here's some interesting information.....got my cam sheet in front of me and...

the cam - overlap @0.050" is 6deg....now when you take into account the clearance between the shim and cam (this is 0.012" rather than my current 0.009")...overlap @ 0.050" is -1deg

i must have mis-heard the cam guy when he told me the overlap

very very interesting indeed.....so what do you all think i should do with my cam gears? perf? install?

If it was my me doing it...I would first try retarding both...play around with retarding the intake 3-4 degrees, and the exhuast around 2 degrees...that will effectively close overlap a little, and see where you stand...If that saps large amounts of power, try opening up a little more overlap...

So first off...Intake 3 degrees retard, exhuast 2 degrees retard...that could give you an idea...

[Installshield 2]

ok men...

I think I have been able to sift through some other sources crap know where the contradictions are coming from...

Overlap...

This is what is causing all the crap...No two engines respond the same way to shifts in overlap...and this is the fundamental reason why you see some claims that advancing intake timing causes better lowend or high end...put simply it is different from engine to engine...

This is what overlap does...overlap allows a scavenging effect in which the vacuum of exhuast pulls fresh air and fuel in to the cylinders...But it is extremely tricky, and has a very exact threshold...Too much overlap will always hurt lowend, in which the piston speeds (and thus the valvetrain movement) is too slow and allows the exhuast system to suck fresh air and fuel out of the head (the fresh air and fuel basically goes in through the intake valves and immediately out through the exhuast valves if there is too much overlap)...the "right" amount of overlap needs to be applied to where you want the powerband...If you have way too high amount of overlap, it will not help in any rev range and cuase a loss of power all over...if you have no overlap at all high rpm breathing will be a disaster, and low rpm power would not be as good as it would with a small amount of overlap...the scaveging phenomen (in which the exhuast vacuum pulls the intake charge in, but then the exhuast valves shut just in time to let nothing "fresh" out...it helps with volumetric efficiency) will only happen on most engines for a few thousand rpm...and that is usually where you will want your powerband to be...so you need to dial in the amount of overlap you want in relation to where you want your powerband to be...then overall you will have the timing advantages of exhuast blow down, intake ramming, and overlap scavenging working together in your powerband to make maximum power...

But we can apply this, since we FS owners need relatively low amounts of overlap...

Advancing the intake cam should help with high end power, it will better utilize the raming effect and overall high rpm breathing...This is usually the case with long runner'd intake systems such as what we have...Now this gets tricky becuase this also increases overlap, and too much will start to kill off high rpm power (actually power everywhere) by allowing to much fresh air and fuel to escape directly into the exhuast system...So sometimes you see engines that take a 3 degree advance of the intake cam and make very good power up high...but my guess is that on a engine that does not like too much overlap, it will hurt the power over the entire rev range...but not becuase of the advancing of the cam itself, but more becuase of the increase in overlap...

But the goofballs that do the report on the tming for that particular car say "Advancing the intake cam makes better lowend power"...which is misleading, and one reason why we seem to be struggling for a definative answer...

The same can be applied to retarding the intake cam...in which this decreases overlap...this will in general move the power band down, but if the decrease in overlap makes that particular engine happier...it will sometimes just make the overall power band bigger...making it start lower, but sustain itself all the way through redline...

Basically this is what we can assume on an FS so far, and lets apply this to an engine with zero overlap...Advancing both the intake and exhuast cams identically will move the powerband up relative to the amount of advancement...we know that advancing the intake cam, overlap issues aside, helps with higher rpm...same with advancing the exhaust cam, overlap issues aside...So advancing both iliminates the overlap problem becuase it keeps it the same...obviously the said engine will at least have a little overlap, and the amount of overlap will be just as much of a variable in determining the powerbands location and peak output...

Retarding both the intake cam and exhaust cam will move the powerband down, normally and again overlap can cause this to be erratic...

So hopefully you can see how this affects what other people claim though...overlap itself can cause very different things to happen to the powerband of the engine...so we really won't know for sure until enough of us get the gears and play around with them...

[twilightprotege]

good info install...yeah you can see how much trouble i found when i was trying to find some decent information on what to do...

a little more info on my cams (@ 0.050") :

exhaust - closes 1.4degrees ATC, intake opens 4.6deg BTC. now what is cam specs, not what the valves are actually doing. so yeah, that's where the 6deg of overlap comes from

now the valve events (@ 0.050") :

exhuast - closes 1.9deg BTC, intake opens 0.9deg BTC, so that's where i got the no overlap (-ve 1deg overlap)

so yeah, will try retarding intake 3deg at first, and exhaust 2deg and see where that takes me....gotta get some dyno time!!!

[Turbo Matty P]

I'm almost wanting to pay for your dyno time so you can save me money on mine when i do it! Once you lay down the initial cam timing specs on the FS motor it should be easy for everyone to have a starting point. Also, are you doing this with stock cams or mazdaspeed cams? I really want to see a head-to-head of these!!

[twilightprotege]

i have custom cams. a decent bit bigger than j-spec etc...here are the cam specs : (pls not this is not exactly valve events due to the clearance between the cam and shims - i've had mine redone to 0.009")

lift (intake and exhaust) 0.351"

duration @
.010" 273deg
.020" 250deg
.050" 226deg
.100" 199deg
.200" 147deg
.300" 83deg

[thewrench]

Alright, I printed all of perf's info out and read it today at work, and quickly realized that I have been a complete moron. (hand) I had completely disregarded the relationship of where the piston was in its stroke to when the valves were opening. And so now I think your original post, Andy, is wrong in regards to the " moving (intake/exhaust) gear only " instructions. Give me a little time and I'll post up some drawings to show what I mean. (I deleted my earlier cute little illustration) Let me also say that whatever inferences come out of all of this discussion are probably not going to be general. I don't think what is going to work in your situation will work in ANY body else's situation. But maybe at least we can work out a way for people to figure out where to start. I also think that techs at Sunbelt and Tripoint will probably see this thread and chuckle because they figured this shit out a long time ago. One question for you first, Andy, do you know at what points your cams open and close, ie, in relation to BDC and TDC? That info would definitely be helpful. I'll post up again later.

James T

[twilightprotege]

we all certainly got our wires crossed at the start of this thread...hell 5 pages of posts and we're all just starting to understand it. my problem was i was thinking the intake cam would work then the exhaust...but it's the other way around in terms of overlap

yeah, info on btc is 3 posts above yours

[thewrench]

D'oh, I see 'em now. Thanks. The funny thing is, I'm spending all of this thought trying to figure out what you should do, and it ain't going to help me at all. Different head, different cams..blah, blah...

JT

[twilightprotege]

LOL!!!! hey i dont mind ;) anyway, it will help you. yes i have bigger cams - mainly more duration - you can just adjust your cams to similar overlap as what mine will be getting. it'll be a very good reference point for you. it's always good to compair results as well.

[perfworks]

Thats why i posted all this info. So we can all learn. They at tripoint and such had to learn also right.?
So this a good a place as any for all to be a little more knowledgable come time to order thier own products.
Good work guys:)

[twilightprotege]

so perf what are you thoughts on how i should adjust my cams when i get the cam gears?

[thewrench]

OK, so here's my little drawing. BTW, this does not accurately show twilight's cam #'s. This is just to show the effects of changing cam timing on overlap.

http://www.mazdamp3.com/members/thewrench/curvesmain.jpg

So as we see, when changing ONLY the exhaust cam, advancing decreases overlap, retarding increases overlap.
And vice versa when moving ONLY the intake cam, advancing increases overlap and retarding decreases overlap.

The actual effect on performance I think remains to be seen. There are just too many variable to accurately predict, turbulence in the combustion chamber, flow rate of the head, flow of the exhaust.

So when we come to your head, Andy, I have to wonder about that seemingly low # on the exhaust flow. I wonder if between that and your relatively stock exhaust, that you aren't scavenging any exhaust gases at lower rpms and may actually be building positive pressure in the combustion chamber, therefore not allowing air/fuel charge into the chamber. So my question is, do you retard exhaust timing to allow more time for gases to exit, or do you advance, and hope that more gas flows out because you have more lift earlier in the stroke. This doesn'y really take into effect intake timing, but I think either way you'd want to retard it some. I guess my thought was either to retard the exhaust timing ALOT, and retard the intake timing a little less, or advance the exhaust timing, and retard the intake timing, which would reduce overlap. The latter was my first choice, although it seemed counter-intuitve to advance the exhaust, I'm thinking it would give more time to exit gas at higher lift, and it reduces overlap, which looks right.

And the final option would be to retard both, but do the intake a little more than the exhaust, say intake -4degrees, exhaust -2degrees. That would still reduce overlap, but I'm not sure if it would solve the exhaust problem. As for low rpm torque vs. high rpm power, I haven't noodled that out yet, my mind's pretty much fried right now.

Anyway, y'all have fun proving me wrong now. :D

JT

[twilightprotege]

very accurate graph. that's exactly how everything works!

at the moment i'm guessing my engine is having problems because of two things.
1 - the exhaust. the air can get in there quicker than pretty much any other NA P5 around, but the air cant get out....well it gets out, but slowly, so really it needs more time to get out, and 2
2 - overlap. once again exhaust related, but because the car redlines at 6500rpm, i'm not getting the full benefit til redline...if the car reved to 8000 i'd be much happier.

so mainly due to point number 1, i'm going to try advancing the exhaust by 2 degrees and retarding the intake by 2 degrees. advance the exhaust to have the valves open more at BDC to get more of the gases out, and retard the intake to reduce overlap mainly.

what do you think of that?

[thewrench]

Yep! That's what I'm thinking, heck, I wouldn't be surprised if you went way more than 2 on the exhaust.

You know, you may want to go back and change that first post again, this is confusing enough, without having the first post be pretty much the opposite of what we;re saying now, lol.

JT

[twilightprotege]

LOL. yep, will go back and change that now.

yeah i was thinking 2 deg advance on the exhaust would be a good starting point...will prob end up more.

i cant wait to see what the dyno testing and tuning comes up with. that'll be the most interesting part of this whole exercise

[thewrench]

Hehe, yeah, it'll be exactly opposite of what we're thinking. All of this talk is making me want to go ahead and play with mine, I just don't have time right now, or $$$. Can't wait!

JT

[twilightprotege]

you could always try the butt dyno and timing it. ie go to a place, time how long it takes to go from 30mph to redline in 3rd or something. adjust the gears and try again. a relatively accurate way to do it considering you're only doing it in 4rd

[Installshield 2]

holy crap I am having a hard time keeping up with this...every time I check the thread it grows by over a page...

Good graph JT...that hopefully destroyed some confusion...the on paper terms of advancing and retarding timing most likely came from someone using the power stroke as first in the 4 stroke process...But some websites use the intake stroke as first, which skews everything...they still refer to advancing or retarding as the same thing, but if you try to put it together in your head it does not make sense...(in regards to overlap increasing or decreasing)...

I agree with you Andy, a butt dyno will give an idea of where the power band is going to a certain point...If you move your powerband too far down, you will know it when it starts to strangle again at high rpm...

It may be tricky though if the adjustments hurt the power everywhere, but only by about 5 whp...a full dyno session will still be needed most likely for the most accurate adjustments...

[twilightprotege]

yeah, a full dyno session is definately needed. what a few places in the internet say about tunning is play with the intake first. adjust it by 2 degrees and if it makes more power where you want it, keep on adjusting it that way until it looses power. if it looses power straight off, dont keep testing in that direction.

then move on to the exhaust cam and do the same thing. when you know the best places for the intake and exhaust alone, you try and marry the two together. chances are the final result will be somewhere between not adjusted at all the the best for intake exhaust.

a good tuner should know this, if they dont, they are either hopeless or trying to get more money out of you

[Installshield 2]

good points Andrew...

I read that you should start by first moding the cam that is on the end of the engine with the most work...so in your case definately the intake cam...but if you only had a long tube header and exhuast, you should mess with the exhuast cam first...

Preferably the cam timing and cams are the last things to be modified...They sort of complete the engine mods and make the powerband exactly where you want it...

But you are in good shape I believe...even after you add more mods, the cams will just become even more suitable...

[thewrench]

Yeah, that's the hell of it for him, he can spend time and money tuning it now, but every mod he adds later will just make him have to do it over again. It wasn't really planned, but I suppose that's the advantage to doing it the way I am, gathering pieces over time and throwing it on the car virtually all at once. It just takes patience, sweet patience, unfortunately I have very little. :)

JT

[twilightprotege]

yeah i dont have patience! hehehe

i dont mind having to tune it everytime i get something done to the car. yes it does cost me more, but i'd only do tuning on major improvements like exhaust, intake manifold, turbo, haltech puter...that kinda stuff.

yeah i didnt really mod the engine in the way a professional would have, but i pretty much know exactly what i want to do and what i want to get out of the engine, so it makes choices much easier.

hopefully i'll get the cam gears b4 xmas, as soon as i get them i'll let you all know. i need to also work out how to make the head cover part detachable over the cam gears so they can be easily tuned....easier said that done that's for sure!

[curt2go]

Nice and confusing as cams always are. Now that its all straigtend out lets find a good place to get all the stuff to make this happen. The CAMS and the adjustable CAM GEARS. Where are you guys geting all of this. Corksport has only the intake cam and no gears. So lets find out the bst place to get all this stuff. I think I missed a GB on the Cam gears as well so that sucks.. Thanx for all the info guys. TTY

[akhilleus]

tripoint engineering do u search

[twilightprotege]

curt - try talking to jeff at propartsusa.com (that's his nick). he might start up another GB for camgears

[curt2go]

Thanx Twilight. Will do.
OT: Hey twilight I was just in your country for 36 hours. Had to train you military on our equiptment. Very long trip for 1 day..:) TTY

[bill]

See http://www.sportcompactcarweb.com/insidetechnology/0208scc_insidetechnology01a

[curt2go]

Very nice. That helps.. ALOT. TTY

[Installshield 2]

that link is the same thing Andy provided...His was from import tuner, which is owned by the same parent company....The article is the same as the import tuner one...

Both you guys, good find...that should help explain it better than we can...

This post was just in case it confused anyone that the same article is coming from two sites :D

[akhilleus]

very interesting article. unfortunately it didnt show much improvement over baseline. This could be cause of the FI effects. however i think in twilights case it will be perfect since he could dial the power band lower.

[twilightprotege]

36hours? thats not a proper stay!!! hehehe


in that test with the turbo, you'll notice how much torque can be changed around. that's what you're really wanting to look at for maximum acceleration. and there is always the possibility that the engine tested was already close to optimal settings...ie cams suited to the config etc...

hopefully i'll hear from jeff - propartsusa.com - saying the gears have been shipped very very soon.

[curt2go]

When do you plan on getting them. When you do get them will you be installing them right away??? TTY

[twilightprotege]

i havent heard back from jeff, but i was hoping they were shipped on thursday/friday last week, or monday this week. i will install them almost straight away as it's no biggie, will adjust the timing as i've stated and see how it goes. within a month i'll figure out a way to cut the head cover so i can access the cam gears nice and quickly. once i've done that, it'll be straight to the dyno tuning place

[thewrench]

Found this little tidbit, just for info to add to the databank (bottom of page)

http://ca.geocities.com/race_miata/mymod/camgears.htm

twilight, you get your gears yet?

[twilightprotege]

nah still dont have them. i've received something from canada already that was sent after the cam gears (apparently). as usual, jeff @ propartsusa.com wont reply to my private message.

if i dont get them today or tomorrow he'll be getting rather inundated with private messages and emails.

i'm at work at the moment so i done have time to check the link - will do that tonight.

[SFC01v2]

Twilight,

What was your reasoning in doing cams/gears before exhaust?

You probably have more scope to play with power band location and peakiness with the exhaust than cams (in my journeyman opinion). Timing and duration of overlap requirements will be hugely dependent on local pressure conditions on the exhaust port side of the valves, which is again hugely dependent on exhaust primary size and geometry.

There are quite a few books available by Philip Smith on exhaust and intake manifolds for internal combustion engines. For a pretty deep understanding they would make a good starting point (so I'm told as I don't have that deep understanding!!)

[twilightprotege]

it's because i'm still deciding if i'll go turbo in the near future or very later or even never. i dont want to pour a lot of money into a full exhaust then get rid of it.

the exhaust will definately help. there is no doubts about that. the scavaging effect of a free flowing exhaust would be great.

atleast the cam gears will help now. i'm hoping to be able to tune them in and get around 120whp.

[SFC01v2]

Excuse my ignorance (I've only been an Astina owner for 6 months) but where is the greatest restriction in the OE exhaust?

[twilightprotege]

the header and around the rear axle (crappy bends)

[SFC01v2]

And hence your reluctance with the headers...

[twilightprotege]

yeah - i'd want to do the complete system to get the full benefit

[akhilleus]

Thats weird about proparts since they are affliated with tripoint

a decent cat back would be around $300-400...since u already gutted your 1st cat a header isnt really necessary. Thats what i am running and i have been impressed with it so far....a good exhaust is probably one of the cheaper mods u can do and gives the greatest benefit for the price on an otherwise stock engine.

[perfworks]

Damn

[DooMer_MP3]

Why not buy the header/exhaust and sell it if/when you turbo? You'll get a decent return on it if you change your mind in the near future.

Chris

[iluvmacs]

This seems to be a great thread. In some of the earlier pages Desktop Dyno 2000 is mentioned. I'm trying to set up files for the protege engine (FS-DE) and I was wondering if anyone knew the following specs:

IVO (intake valve opening)
IVC (closing)
EVO (exhaust valve opening)
EVC (closing)

I have the stock intake at 0.341" lift, Duration 198 @ 0.050"
and the exhaust at 0.323 lift, Duration 200 @ 0.050".


Once I get those numbers I still have the problem of getting intake manifold pressure drop numbers. If anyone can help, I'd appreciate it. Thanks.

[twilightprotege]

sorry i only have the specs on my custom cams

[jaman]

This seems to be a great thread. In some of the earlier pages Desktop Dyno 2000 is mentioned. I'm trying to set up files for the protege engine (FS-DE) and I was wondering if anyone knew the following specs:

IVO (intake valve opening)
IVC (closing)
EVO (exhaust valve opening)
EVC (closing)

I have the stock intake at 0.341" lift, Duration 198 @ 0.050"
and the exhaust at 0.323 lift, Duration 200 @ 0.050".


Once I get those numbers I still have the problem of getting intake manifold pressure drop numbers. If anyone can help, I'd appreciate it. Thanks.

I have Dyno2003, so if you want to trade files that would be cool. Though I have to admit, I only got the program today so I don't have much set-up. By the way, I also have Dyno2000.

[twilightprotege]

iluvmacs and jaman, once you two can get dyno2000 or 2003 working with stock specs, i'll give you my custom cam and ported head details and see what they spit out if that's ok with you...

[iluvmacs]

No problem, but if you want it to be accurate, I need not only stock cam specs, but stock head flow bench results. I CAN chuck out results estimating those values, but I can't guarantee the results.

[twilightprotege]

it'll be a problem to find stock info... :(

[iluvmacs]

we can still guess though.

[akhilleus]

why dont u just get it dyno'd?

[twilightprotege]

i'm just curious as to what it says the engine should put out, then compair it to the dyno...would be very interesting

[iluvmacs]

I don't have access to a dyno, and if I did, that would be awesome. However, this program allows you to estimate changes in performance BEFORE you actually buy parts. This allows you to figure out what parts to buy to get the response you want out of the engine.

I agree that actual dyno numbers are the only accurate way to measure an engines power, but I would really prefer to know what's going to happen before I spend $300-500 on parts, and then the money to get the car to a dyno and actually dynoed.

[808MP5]

wow. that took a while to read. 8 pages of very resourceful, interesting, and down right confusing information. but it was like reading a very good book with the last 25 pages ripped out. there was no ending, just the END. thanks for the good reading.