graziano

#2
Don’t know what the “real” spec is but I used 120 inlb for the clutch, stepping it up in increments and running a star pattern. This is for the 9x M6? 70mm bolts. Not sure what the throw out bearing spec is as mine was already installed.
 
#3
Be sure you use good quality bolts for the clutch. I used what was supposed to be good bolts, only to have a couple break. Ordered some from ARP second time around. Insane price, but they actually ARE good bolts...
 
#4
Frank - how the heck did you find broken clutch bolts? By sound or clutch engagement issues?

And what bolts were you using?
 
#5
I had ordered 12.9 socket head bolts from one of the online suppliers. I usually order from www.allensfasteners.com, albanycountyfasteners.com or mrmetric.com so it was probably one of those.

I blew the motor about 200 miles in. When I removed it, one bolt was broke, another broke when removing it (with hardly any pressure so it was already 'broke'). Both broke through the threads even with the flywheel face. I had used a torque wrench putting them in, so I do not think it was an installation issue. The clutch was still working fine. My car was loud enough that you could not have heard a bolt rattling around.

There is a lot of torque on those bolts, and they are quite small. But it's beyond me how I broke two and not all of them. It would seem like twisting the clutch pack would shear all of the bolts at once.

The ARP bolts where bloody expensive. Something like $80-$90 for two blister packs. But no worries about the quality of them now.

Pulled the ARPs out last week (yep, blew another motor earlier this year and just now getting around to R&R). They are fine.
 
#6
When your motor failed do the engine seize such that the driveline would have tried twisting the crank?

Theoretically speaking none of the 9 bolts and holes are perfectly matched. If relative motion occurs between the two sets of holes it’ll make contact only at one bolt, the others have enough positional tolerance to be out of contact. Once the first bolt fails the holes move relative to each other again until the second bolt stops them - then fails. By now you’ve probably dissipated enough energy so the remaining bolts remain intact.

Practically speaking I would think there would be enough yielding elsewhere for more than 2 bolts to make contact before exceeding their shear strength.
 
#7
The engine failure did lock up the drive train (at 155mph). Bent the crank .080. Did not have sticky tires (PS2s), but did have a lot of downforce cranked in.

In any case, they are small diameter bolts. I'd suggest not assuming your every day internet supplier's bolts are actually up to spec. Not that those guys are dis-honest, but they are not making the bolts...
 
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