Puzzling SPEC Pressure Plate Thickness

[rcfanatic]

I have an '86 eta and my throwout bearing died a few weeks ago. I decided to buy a b25 flywheel and a stage 2 spec clutch for late model cars.

After comparing the overall thickness of my old flywheel/pressure plate and the b25 flywheel/pressure plate, the overall thickness of the eta is 3.5" and b25 components is 2.9". The bearings are about the same size.

Shouldn't the pressure plate be larger on the spec clutch to compensate for the thinner flywheel? Is my clutch going to engage correctly?

[rcfanatic]

Update:

The previous measurement isn't the right one. I remeasured from the plane where the flywheel bolts to the crank, to the pressure plate fingers where the bearing rides.

The eta flywheel/PP is 3.3" and the b25 flywheel/spec PP is 3.0".

So will this 0.3" prevent the clutch from fully disengaging?

[psyber_0ptix]

hmm...might also depend on the springs used inside the pressureplate. Maybe smaller movement is enough to disengage. Is there a difference in clutch disk thickness and the clamping disk on the pressure plate?

[blocke]

What T/O bearing are you using? The ETA on or the 325I one?

[rcfanatic]

hmm...might also depend on the springs used inside the pressureplate. Maybe smaller movement is enough to disengage. Is there a difference in clutch disk thickness and the clamping disk on the pressure plate?

The combined thickness of the old clamping disk/clutch is 0.82", the new is 0.9"

Edit: Some of that difference will be clutch wear

[rcfanatic]

What T/O bearing are you using? The ETA on or the 325I one?

Using the TOB that came with the SPEC kit, which is for 325i flywheels. Just seems like an entire eta system should be the same thickness as an entire "i" clutch kit.

Only other explanation is that maybe the clutch has already been replaced... and they used an "i" PP with the eta flywheel

[rcfanatic]

Any thoughts or suggestions? I want to solve this mystery before I put everything back together in case it doesn't work

[jlevie]

Unless the engine is a "budget stroker" you can't use the B25 flywheel as it doesn't have the CPS and Cylinder ID slugs required by a B27 engine management system.

[rcfanatic]

Thanks for the reply. The car has already been converted to an "i" so it doesn't need that crank position sensor. I'm just concerned about clutch disengagement from the 0.3" gap

[jlevie]

In that case if you use an i flywheel, clutch, and TO bearing it will work.

[rcfanatic]

update.. the clutch engages close to the floor and there are a couple inches of play at the top of the pedal. I think it's just not bled completely.. but wonder it's from that loss of 0.3"

[JTapper]

How do you like the SPEC Stage 2? I just picked up the Stage 3, hope to have it in next weekend.