Spec clutch shim measurement

I have my Spec flywheel, pressure plate and stage 2 clutch disc installed on my LS1 with a C5 2-piece bellhousing. And I have the Admin's TT adapter with C5 slave and throwout bearing mounted in the car. I'm now doing the measurements to determine if I require the shim. I found the SPEC video on youtube and am doing my measurements exactly as they do them and it doesn't look as good. I get:

A = 2.56
B = 2.51
A - B = .05

This is considerably less than the spec of .175 to .225. And adding the shim will only make it worse. I'll quote some of SPEC's material.

"If there is no difference between the two measurements, or if "B" is greater than "A", there could be a problem with clutch engagement which could result in premature clutch slip and eventually a total failure. Contact your clutch manufacturer before proceeding with the install."

Suggestions?

Thanks,
Rich

Other people say that B should be 1/16" to 1/8" less than A. But if thats what Spec told you, then you should disassemble the clutch components and check that the pilot bearing is seated and not contacting the clutch disc hub. Also, if I remember correctly, to get an accurate measurement for B, the slave spring must be removed.

Did you clearance the slave cylinder base to fit into the grooves of the BH adapter?

Thanks for the toughts. What I'm getting is nearly 1/16". But the numbers I'm quoting are from the instruction sheet that came with the clutch package. Yes, I have the spring removed from the slave and I'm sure the pilot bearing is fully seated and clear of the clutch disc. As for the slave mounting on the TT adapter, I did nothing with this. It came from TPC assembled and I assumed it was correctly setup. Perhaps I need to pull this apart and give it a little more clearence.

Rich

Sounds to be too close for something to be wrong (major). Yeah, check that the slave is fully seated against the adapter and its flush and torqued down.

Also notice that theres an adapter to torque tube bolt that passes through the slot that index/centers the slave cylinder. If this bolt is into the adapter too far, it will hold the slave out from seating to the adapter flush (see black bolts in picture).



Heres a pic of the mod to the slave cylinder base...

The C5 TOB has to be bolted down FIRST to ensure the torque tube set screws don't put it of kilter. The upper driver's side set screw will protrude rearwards by another 0.200" when looking at them from the rear of the adapter plate when the TOB is bolted down.

That being said, also make sure that the Bleed screw is completely OPEN when doing your measurement. Whatever disc you use, you must verify that the rear hub center clears the pilot bearing by at least 1/2 the thickness of the clutch disc.

I've just pulled the slave, loosened the set screws and re-torqued the slave to the tt adapter. The only difference with mine is an additional relief for the 4th set screw so none of them sit further out. With the spring removed and the bleed screw open I remeasured and came up with 2.52" for B.

So I guess next I pull the pressure plate and check clearance with the pilot bearing. I got that good and seated last night with a .45" protrusion from the crank face. Flywheel is seated and torqued to spec, pressure plate torqued to spec. And I was sure the clutch disc cleared but I'll go back in and verify that and then re-measure A.

So, say that's fine as well and this .05" clearance is all I have. What then? Maybe cut out a ring of .15" thick sheet alumuminum to use as a shim between the bellhousing and tt adapter? Seems like a hack.

Thanks Guys.
Rich

Does the TOB have a casting of D951004?

I think Spec just has their PP splines/fingers protruding more than a factory Pressure plate. What is the distance from the block/BH face to finger/TOB plane?

In the grand scheme of things, just as long as the TOB plastic bearing tower does not bottom out on the lower TOB casting when everything is bolted up, I'd go with it. The Fingers are going to settle towards the engine side after the first few 100 miles anyways.

I dont really see a problem. But, comparing your measurements to mine (I run an LS7 PP and flywheel), they are bit different. Youd think "B" would be similar.
My measurement from PP fingers to adapter plate face "A" is 2.25" and the measurement from the TOB surface to adapter plate face "B" is 2.125" which gives 1/8 inch.

I believe it was 3.24". From memory though and I'll have to check that casting number tonight as I'm on a bus to the city for work now,late...

944-LT1 wrote:Youd think "B" would be similar. ... the measurement from the TOB surface to adapter plate face "B" is 2.125" which gives 1/8 inch.

Yeah, odd. Mine is for sure bottomed out for the measurement. I'll check the part number tonight. Thanks.

Well damn! I gave the thowout bearing a good shove and it moved. Dur... So I've re-measured everything, determined I need the shim, installed it and now I'm right at a .21" gap. Sorry for the waste of time and thanks again.

Rich

Great to hear!

Okay, the engine is in the car! I have bled the clutch very thoroughly and am seeing about 1/4" of travel at the slave cylinder. I'm nowhere near starting this thing so can't really test it and am wondering if that's enough to get good release of the disc. I am using a 13/16" Wilwood master mounted to a Tilton 3-pedal assembly with an adjustable stop on the clutch pedal. I want to get enough disc release for good shifting without over-traveling the slave cylinder. But I cannot find a specification online for the amount of travel. Anyone know?

Thanks,
Rich