C2 - 427 390HP Flywheel O.D. ?

[Tom D.]

Bought a new GM no. 14085720, which looks like it will handle the large clutch. However, Overall outside diam. = a little less than 13"

My old one, cast number 3789783 (possibly 37899733) is nearly 14" O. D. including the starter gear ring.

How is my starter ever going to touch the new one? Did I order the wrong part?

Thanks!
Tom Dingman
4889

[Tom D.]

Re: C2 - 427 390HP Flywheel O.D. ?

Here's something Joe said back in 2004. (from the archives). Looks like I need a 168 tooth flywheel, but now I am wondering where I got the 14085720 number...

The '444' bellhousing is designed for use with a 14", 168 tooth flywheel. The GM casting #3791021 flywheel is a 12-3/4" flywheel and must be used with the appropriate bellhousing. A 12-3/4" flywheel and 10-1/2" clutch were used with ALL 1963-68 Corvettes with small block. For 66-67 the 14" flywheel and '444' and '621' bellhousings were used with 427 applications only.

[Joe L.]

Re: C2 - 427 390HP Flywheel O.D. ?

Tom------

GM #14085720 is a lightweight, 12-3/4" flywheel. It is the SERVICE replacement for the flywheel used for 1965 Corvettes with L-78. It is not the flywheel that you need for your application. You need GM #3991469.

There are some parts references that show the GM PART #3866735 (the original 65 L-78 flywheel) or its successors (GM #3991406 and 14085720) as being applicable to "1966 Corvette with 427". Those parts references, every single one of them, are incorrect. Period.

[John H.]

Re: C2 - 427 390HP Flywheel O.D. ?

Tom -

The #14085720 is the lightweight (15#) nodular iron 12-3/4" diameter 153-tooth flywheel that only accepts a 10.5" clutch, whose only BB application was the '65 L-78 and later L-88/ZL-1. All other BB applications used the standard 14"-diameter 168-tooth flywheel that accepts the 11" clutch.