I removed the clutch inspection cover from my 63 corvette this weekend and I noticed the flywheel casting # 3973455 N (not sure about the last two numbers) but I know it is not the correct 1021 cast part as my parts book calls out. My car is a 63 with a 421 bellhousing and I'm sure a 10.5 clutch. Can someone ID this part? Thanks in advance for your help.
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Re: C2 flywheel
Timothy-----
I think that the number is "3973458 N". This is a 12-3/4" nodular iron flywheel of lightweight (16 lb) design. This flywheel was first issued in 1970 and was one of the casting numbers used for flywheels once sold under GM PART number 3991406. Primarily, this flywheel was used for SERVICE of 1965 L-78 and 1967-69 L-88 and was used in PRODUCTION and SERVICE for 1970-72 ZR-1. However, it can be directly retrofitted to any 63-68 small block application.In Appreciation of John Hinckley -
Re: C2 flywheel
Joe, Thanks for responding to my post. Can you tell me the weight difference between the original and this part and if the cars performance will be affected? I had this flywheel balanced with the engine internals and the pressure plate when I rebuilt it years ago.Comment
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Re: C2 flywheel
Tim-----
I'm afraid that I don't know the weight of the original 63-68 manual trans flywheel. I THINK that it's about 25 pounds, or so, though. The flywheel that you have will provide quicker reving, but you will lose some "from a standing start" performance. For a really good engine balance, you can't change it at this point without re-balancing all the reciprocating components.In Appreciation of John HinckleyComment
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