Race Engine Forum UK

Hi Guy!

Maybe an obvious answer to this one but here we go:

I am about to fit a Helix clutch to a NA 2 liter 8V tc with 131 flywheel - I need some guidence regarding what quality of bolts to use.

Best regards

Remi

8.8 grade will easily take the shear load on that.

G

Remi,
Yes, I agree with GC, as I recently did this with a 7.25 Tilton unit. Are you going to use thru bolts or drill and tap the FW. I did the latter as there were 2x dia. bolt thickness in the FW. Side note: what are you going to use for a clutch release bearing as it is difficult to find an after market one that will accept the 1.020" dia, guide sleeve on the transmission and have a large enough dia. at the contact face?

Ted

You should make sure that the transition from bolt thread to unthreaded section does not line up with the flywheel surface/ pressure plate interface. Ideally you want and an unthreaded portion of the bolt at that interface, to be below the flywheel surface.
Tom

Although what you say is true Tom and it is an ideal from an engineering standpoint - whether it's vital is another matter, it depends largely on the applied torque. I have only once ever in a 7.25" clutch app bothered with it.

I have not included any stress concentration factor in the calc below - if my math is right - you can see the torque from an atmo 2 liter 8v is unlikely to lead to any problems even if (as I cite) the shear load at the joint of clutch cover to FW is taken entirely on the threads.

G

THREAD INTERRUPTED 31 MAY 12 BY SERVER PROBLEMS -- CATCH UP BELOW..

Guy,
Great spread sheet, thank you for doing that. I may be a bit overboard on this one, but I hate pulling a trans or an engine because of a broken clutch. So I am ultra-conservative on this subject.
I have had my fair share of broken clutch disks, that were rated for far more torque than my VX engine puts out, so I am ultraconservative in this area. Besides, what is the actual driveline torque / shock / stress on the bolts when you let your friend drive your car and he dumps the clutch? I don’t know the answer to that one, my friend always says he didn’t do it!
Scarey thing is, sometimes that friend is me.
Tom

Understood Tom

Standard induced preload from 14-16lbf ft (assuming adequate bolt thread & underhead lubrication) should be sufficient to withstand the kind of shock & cyclic load you refer to. That joint stiffness calculation is a lot more involved and I have never had to do it with this application and hope not to have to start now!

G

REVISED CLUTCH BOLT SHEAR LOAD SPREADSHEET

GC