Failed piston ring?

Kooldino

MOTM Winner Jan '09
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So yesterday, DiS and I did a compression test on my motor. Now for whatever reason, both on my built motor and my stock motor, I always ran 140-150psi on all cylinders instead of 180. Maybe my tester is off. But it's always consistent.

Anyway, so we checked my cylinders. They all ran 140-150 with the exception of #3, which ran 95 or so. So we dumped a teaspoon worth of oil into the cylinder to try it again, and it hit 120psi.

Now IIRC, a teaspoon of oil added to a cylinder should only increase its compression by ~10psi. If it's anything more than that, chances are you have a damaged piston ring. Since the difference was 25, I'm going to have to lean towards that.

So here's the deal. Monday morning, I'm going to call JE and try to have them ship me some replacement rings ASAP. Hopefully they can actually get them to me this week.

After that, I'm going to have to dissasemble the ENTIRE motor in my car, in my garage. Fortunately, DiS has offered to help do it all next weekend and crash on my couch.

We're going to need all the help we can get. It's a big job to do in one weekend. Any volunteers to lend me a hand? You're welcome to crash here. I'll begin work as soon as I get the parts I need this week...so maybe Thursday (all day), Friday (from 6PM) through Sunday night. I live 15 minutes from Atlantic City. Act now and get all the free Pizza you can eat! :)

Any advice from anyone who has replaced a piston ring with the motor in the car (idgrasil)? Will the trans have to be unbolted/taken out?

The list of parts I'll need AFAIK:

RECEIVED - new head gasket
RECEIVED - ARP 11mm head studs (i have the 10mm head studs now)
RECEIVED - New set of rings (might as well buy two just for the hell of it)
ORDERED - New TB gasket
RECEIVED - New gasket for the driver's side coolant hose (where it bolts to the head)
A pack of razor blades to clean off RTV
RTV
Someone should probably bring a camera/video camera
A drill and a set of drill bits
RECEIVED - Piston ring tool - the ones that allow you to slide the piston in with the rings
Does anyone have an impact wrench?
Anyone have a radio/cd/mp3 player that plugs into the wall? Because I mean, seriously, DiS can't sing.
...anything else?

Also, does anyone know if the car is drivable? Will I damage it if I'm driving it with a bad ring? (or worse, a damaged piston??).
 
that sucks man, good luck on the rebuild. At least you got some help.
 
man sounds like to what happpened to me...
except i had 30 psi in #3 not 90.

I bet your studs are failing man and you are loosing compression into your water jackets.

I would keep an eye on your coolant temps if you could. Also take off the rad. cap and watch for air bubbles come up. if you see them then you may be losing that compression into the coolant.

damn 10 mm studs!

-Bryan
 
ps i put the new head on with new gasket and 11 mm studs. Thumper is running and making 210 psi on all cylinders. I couldnt be more happy.

Take the studs out and get the 11s. You will save yourself a lot of guess work and headache later. TRUST me.


-B
 
azian6er said:
man sounds like to what happpened to me...
except i had 30 psi in #3 not 90.

I bet your studs are failing man and you are loosing compression into your water jackets.

I would keep an eye on your coolant temps if you could. Also take off the rad. cap and watch for air bubbles come up. if you see them then you may be losing that compression into the coolant.

damn 10 mm studs!

-Bryan
kooldino, you did use stock studs in you re-build correct?
 
yes he did use the 10mm arp's aka death

pull the head man change the studs new gasket and your compression will be good i believe. But i would inspect the piston rigs of courseas well.

-B
 
As far as needing to take your trans off.... no you don't. You can just slightly seperate the trans from the motor just to take off 2 bolts that are holding on the main bearing support that are just behind your flywheel. You will have to take your top end off, oil pan, main bearing support and then you can get access to the rods. Once you take off the rod caps the pistons can be pushed out the top of the block. If I lived close to you I would definetly help out but I'm about half the pacific ocean away. :D Good luck and don't get to frustrated when/if things don't go how they should!

Dave
 
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PRO 5 said:
As far as needing to take your trans off.... no you don't. You can just slightly seperate the trans from the motor just to take off 2 bolts that are just behind your flywheel. You will have to take your top end off, oil pan, main bearing support and then you can get access to the rods. Once you take off the rod caps the pistons can be pushed out the top of the block. If I lived close to you I would definetly help out but I'm about half the pacific ocean away. :D Good luck and don't get to frustrated when/if things don't go how they should!

Dave
You got a beautiful car man!
 
What type of ring package do you have now?What type are you getting?
Different ring packages require different RA reading to seal properly.

See if you can find a Profalometer(Gives you the RA) and take a few readings in the cylinders.Then look up what you need.

On all our high HP setups we have the pistons gas drilled.This helps the pistons seal under high boost loads.
 
you can drive on it, but you might want to get those cylinder walls bored so its a fresh start.
 
i drove on my cracked piston (and charred rings) ONLY since i HAD to... about 15 miles. The CEL was flashing on/off (misfiring)
 
mp5jeff said:
then sleeve it :D
lol, sleeves are for hondas. Anything more than a slight hone, the block has to come out of the car. When I twisted my rod we rebuilt the engine in car. Let me tell you it's a hell of a job. The only major hickup was removing the oil pan. They did it without removing the tranny, by drilling a little access window to get to two bolts.
 
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