427 clutch and flywheel

[John McRae (30025)]

Is there any advantage to using an 11" vs. a 10 1/2" clutch and flywheel for this engine. Does anyone have the p/n for the standard flywheel and is it 10 1/2 or 11" .
Thanks for any help.

[Joe Lucia (12484)]

Re: 427 clutch and flywheel

John------

All Corvette 427's, except L-88/ZL-1, originally used a 14" flywheel. All Corvettes 427's, except L-88/ZL-1 and 1969 with MA6 clutch, used an 11" clutch.

Basically, I think that the 14" flywheel/11" clutch is the best way to go for a big block; that's what I intend to use for my "ZL-1" project. The current GM part number for the 427 flywheel is GM #3991469. This flywheel is just like the original except that it is dual-drilled for use with both 11" and 10-1/2" clutches. Using it with a 10-1/2" clutch makes little sense, though, since the primary reason that the 10-1/2" clutch is used is to allow the use of a smaller, lighter 12-3/4" flywheel. If you're going to use the 14" flywheel, then you might as well use the 11" clutch.

For street operation, even with a relatively high torque big block engine, I still think that the standard weight, 14" nodular iron flywheel is the way to go.

The vast majority of 1969-81 Corvettes, big block and small block alike, used 14" flywheels with 11" clutches. There were VERY few exceptions.

[John McRae (30025)]

Re: 427 clutch and flywheel

Thank you Joe.

[Clem Zahrobsky (45134)]

Re: 427 clutch and flywheel

i always use a 10 1/2" disk with the 11" clutch because using the 11" disk allows the lining on the disk to fray on the outside edge and make for hard shifting because of the drag. we also trimed the OD of the 10 1/2" disk down about 1/4"