Shaved head and re-pinned Intake cam

[PR5Matt]

Has anyone shaved their cyl head to raise compression instead of going to the JDM pistons? If so, how far did you go? I want to put the JDM intake cam in my car and re-pin the stock intake cam for the exhaust side. How difficult is this mod, and does anyone have pics and specs needed to show how to do it?

[curt2go]

Shaving the head depends on two things. How thick the base of the head is. If it is thin already shaving it will hurt the structural integrity. If it is think then the only other thing to consider is the piston to head clearance. This should be fine but I am not sure.
Probably every .010 that you get it shaved it will increase the compression by 0.1 points. Approximately. The guys that know these motors well will know the exact numbers..
The cam reppining is up in the air i think. One person had it done and said it would not work so he did not have it put in. BUT this is what the mechanic said. Twilight still says it can be done. So wew ill have to see if someone can get it done succesfully. Keep us posted.. TTY

[njaremka]

It can be done, but you will need adjustable cam gears, too. With overhead cam engines, when you shave the head, you change the effective length of the cam belt. Without adjustable cam gears, getting your cams in the right spot will take more work.

[akhilleus]

Yeah it fell through. Dont bother with it. The gain is probably minimal. I am having a custom exhaust cam ground. I would recommend the same for u.

[curt2go]

akhilleus how much will it be to get the custom cam done for you. Would you consider doing more than one? What specs are you going with?TTY

[akhilleus]

I was considering having multiple ones done. I am figuring less then $200. It will have these specs
212-215deg duration
.344-.350 lift
I contacted a place last night and i am waiting to hear a response. I am sure the repinning can be done .... but with the problems involved( finding a place to do it, precision with the drilling(it would be off by a couple deg...meaning cam gears)) Also i had my cams retarded by about 5deg by moving the cam gears by one tooth. This definately helped my midrange/lowend and my launches. I might keep this setting with the exhaust cam installed but I will try it both ways.

[curt2go]

You don't think thats too much duration? When do you plan to get it done?TTY

[PR5Matt]

Originally posted by njaremka
It can be done, but you will need adjustable cam gears, too. With overhead cam engines, when you shave the head, you change the effective length of the cam belt. Without adjustable cam gears, getting your cams in the right spot will take more work.

I am aware of that. On an SOHC engine it usually retards the cam. Dohc would be a little similar. I am a mechanic, I just ask these kinds of basic questions to get a feel for what others have done and what their experiences were. I thank all of you for you help!:D

Also, if you shave to far, and if the 2.0 started out non-interference, it just might become an interference engine.

For you four cyl guys, check out the homemade working of theMerkur xr4ti I am working on:
www.geocities.com/mattsstang87

No if somebody could give me an example of how mcuh they tried to shave their head... (I know, I'm lazy)

[PR5Matt]

Originally posted by akhilleus
Yeah it fell through. Dont bother with it. The gain is probably minimal. I am having a custom exhaust cam ground. I would recommend the same for u.

I was figuring that the gains might not be worth it. I figure at the level these cams are, it would be best to just install the JDM intake. Just wanted to know what you guys have experienced.

[PR5Matt]

I asked about pics and specs for the pinning because I have a mill, lathe, etc. in my garage. Was going to try it if it was worth it.

[akhilleus]

I would think it might be better to get either the FP-DE pistons which will raise comp. to 9.7:1 which our ecu's can handle. Or maybe a thinner head gasket. shaving the head wouldn't be worth it IMO... i think u need a drill press... and something u can use to measure the angles. Good luck but i think it would show much more gain if u have a cam custom ground... twilightprotege might have info too.

[twilightprotege]

i dont think shaving a head is worth it. too much trouble. new cam belt, new head bolts, possibly problems with oil and water coolant jackets, possibly line up problems with the gasket.

the much safer option is to get HC pistons if you want to go that way...

matt if you're going to repin the intake cam, you basically need to have the old exhaust cam out at the same time, work out exactly where the pin should be for the exhaust side and drill. it's not overly difficult, but you will be out by a few deg almost for sure.

[PR5Matt]

Originally posted by twilightprotege
i dont think shaving a head is worth it. too much trouble. new cam belt, new head bolts, possibly problems with oil and water coolant jackets, possibly line up problems with the gasket.

the much safer option is to get HC pistons if you want to go that way...

matt if you're going to repin the intake cam, you basically need to have the old exhaust cam out at the same time, work out exactly where the pin should be for the exhaust side and drill. it's not overly difficult, but you will be out by a few deg almost for sure.

That's what I figured (about the re-pinning). As far as everything matching up after milling the head, just don't go overboard and you'll be okay. Especially on an in-line engine. Now on a v-8 or v-6, that can be alittle more difficult to make sure everything mates up if you go over 10 thousandths...

[curt2go]

Hey PR5Matt since you have all the equiptment will you be trying the re-pinning? Let us know how it goes. You may be doing more than 1... :) TTY

[hi-perf]

Originally posted by akhilleus
I would think it might be better to get either the FP-DE pistons which will raise comp. to 9.7:1 which our ecu's can handle. Or maybe a thinner head gasket. shaving the head wouldn't be worth it IMO... i think u need a drill press... and something u can use to measure the angles. Good luck but i think it would show much more gain if u have a cam custom ground... twilightprotege might have info too.

FP-DE's have the same compression ratio. the difference between the FP-DE and the FS-DE is that the FP-DE is a de-stroked version of the FS-DE.

Compression remains the same, the only thing that really differs between the two is the ignition coil pack, crank and rods. Also the tranny used (though the G15M-R is compatible, but not compatible with 1.8 axles) and axles are different.

[akhilleus]

Actually the pistons from the 1.8L FP-DE @9.1:1 are higher compression when used in the 2.0L@9.7:1 with oversized rings. They are stock pistons in the Australian and European models. Unfortunately no one has used them so far except for when they were stock equip. If you are willing to invest in engine management then u have more options like the 10.4 and 10.7 but they wont show much in gains w/o tuning. Its an unfortunate fact that the a-spec ecu cant take advantage of HC pistons above 9.7-9.8:1. So the fp-de pistons are the only "easy" option. they're cheap too.

[PR5Matt]

Originally posted by curt2go
Hey PR5Matt since you have all the equiptment will you be trying the re-pinning? Let us know how it goes. You may be doing more than 1... :) TTY

Yea, I was thinking about giving it a try, but I don't believe in going into anything blind if I can get advice from someone who may have tried it before. Intelligence before pride...

[Kooldino]

Originally posted by njaremka
It can be done, but you will need adjustable cam gears, too. With overhead cam engines, when you shave the head, you change the effective length of the cam belt. Without adjustable cam gears, getting your cams in the right spot will take more work.

Good point. So you can adjust your cams to make the belt "taught"? How?

[Kooldino]

Originally posted by PR5Matt
Also, if you shave to far, and if the 2.0 started out non-interference, it just might become an interference engine.


That's part of the reason I don't have a high lift cam yet. :)

[Kooldino]

What does "re pinning" the cams mean?

[curt2go]

Taking the old intake can and having it re-pined so that it will fit into the place of the old exhaust cam. Giving about .020 more lift.. Cheap and dirty way of getting a mazdaspeed exhaust cam.. TTY

[Kooldino]

Where are the pins??

[akhilleus]

on the ends of the cams