James Bailey

NOPE

James Bailey

Moldex made many of the early stroker cranks, Scatt did them for DEVEK and some for 928 International. Slight differences in design. The material and workmanship was much higher on the Moldex cranks however there are some problems with the basic design.
Greg started with a clean sheet of paper and rethought the crank design and now has made it lighter, stronger, faster for somewhat LESS than six million dollars !!

jcorenman

I thought Mark's car had a Tilton clutch with a "pusher" slave cylinder. But I might be wrong, it happens often...

IcemanG17

Sean
I believe the crank I dropped off at the machine shop is a Devek era Scat...its stamped 3.75" and has 8 full counterweights. The main bearings are standard 928 size but the rod bearings are SBC..... It is cross drilled, so both side main bearings oil the rod bearings. I didn't weigh it, but damn was it heavy

I think your other 3.59" crank is a moldex, likely 6 counterweight....

IcemanG17

This also is correct.......more like a lightswitch.....but super light and strong....

MGW-Fla

Depressing to see this. Thanks for the autopsy Rob, was very educational, even for a non engine builder like me.

Mark Anderson

Well since its no longer my car I'm not sure I'm the one to answer but I've seen no bad info so far .

James Bailey

Pretty much the ONLY way to get a pressure plate to move away from the flywheel involves pulling BACK on the pressure plate to create clearance for the friction discs to not drag on the flywheel..... that pull is directly on the thrust bearing. Just how it is....

69gaugeman

99% of the cars out there use a pivot point on the pressure plate and so are 'push' to release. In fact this is the first ever clutch I have seen that is pull to release.

A simple (well not realy simple) change in pressure plates would change it so that it would be push to release. I was looking at designing a pilot/release bearing for the 928 and get rid of the lever and that plastic bushing. The pull to release complicates that immensely.

namasgt

Wouldn't the push to release also push the crank against the trust bearing?

dprantl

That is what Jim is saying. Only if the release bearing was mounted directly to the crank (or flywheel) would it not have the crank put pressure on the thrust bearing during clutch release, and I don't know if a setup such as that is possible. Since the pressure plate is bolted to the flywheel, which is bolted to the crank, bolting the release bearing anywhere else will squash the crank and thrust bearing together.

It's possible that the pressure required to release the clutch on this modified setup may have been too much for the thrust bearing and block in a racing environment.

Dan
'91 928GT S/C 475hp/460lb.ft

namasgt

Here is the setup on the corvette, looks like they mounted the release bearing is mounted on the drive shaft with hydraulics pushing it.

http://tech.corvettecentral.com/2011...-installation/

namasgt

Does this engine have Alusil coated bores with 968 pistons?

Imo000

The forces are the same as the porsche setup.

Mark Anderson

Yes it does