Bolt and Washer Sizes? OEM or Parts Store?

[Ads912]

What size are the bolts that fasten the flywheel to the engine (2.4T) and the pressure plate to the flywheel?

Do either require washers?

Is there a difference in quality between Porsche OEM hardware and the nuts/bolts at the corner parts store?

It's time to start turning the wrench on my '68 2.4 project!

Thanks,

[Doug Zielke]

Oh boy...wait 'til Warren gets ahold of this one!

[Mike Feinstein]

Hardness.

I suppose Warren will go into more detail

[Superman]

Indeed. Let me lay the foundation. Flywheel and pressure plate fasteners are indeed special. They spin 100 times per second at red line. Not only are they special bolts, they should not be re-used. Particularly the flywheel bolts, they say.

Spendy as they are, I probably wound trust nothing except factory bolts. But perhaps someone will educate us on using substitute hardware.

[rcwaldo]

The saying is true for hardware as well......There is no substitute!

[Jim Sims]

The pressure plate uses nine M8 x 42 mm long metric grade 8.8 socket cap screws (PN 900.067.090.02) each with a hardened steel helical lock washer (PN 900.027.015.01). The flywheel uses six high strength (I don't know the grade) M12 x1.5 socket head cap screws (PN 911.102.171.00) with a special thinner head containing a 12 point internal wrenching socket. There is a single reuseable washer plate under these screws. The flywheel screws are replaced every time the flywheel is removed as they are tightened beyond their yield point (so called stretch bolts) and it is wise to only do this once. Some people reuse the pressure plate bolts in the lower power (T) applications but if its a 2.4 E or S they are renewed with the installation of a new disk and pressure plate. One really should use OEM fasteners in these applications as the consequences of an inferior fastener are serious. Beside the already mentioned rotating stresses there can be the problems of screw head clearance, rounding the wrenching socket during installation or removal of the flywheel screws or the even worse nightmare of twisting off the screw in the crankshaft end! Use the correct drive bit (Pelican sells them: PEL-TOL-1170 along with the screws: C-102-171-00) in good (sharp) condition; have a second person apply pressure to the bit while you are loosening or tightening the screw with a breaker bar/ torque wrench. Jim

[jluetjen]

Flywheel bolts are up there with con-rod bolts and head bolts as being special applications. They often will also have special features which make them specific for the application. I doubt that you'll be able to find a matching bolt in your local hardware store if you tried. So I'd use the Porsche spec. bolts.
The only exception to this is in some cases ARP bolts can be used since their technology and reputation are high enough for the application. Carroll Smith recommends their products for race applications.

Why bother taking the risk and doing all of the research to use an alternative, I'd get the Porsche parts since they're available.

[Ads912]

Thank you for the info. I thought it was a critical area and you confirmed it. OE hardware it will be.