1963 Flywheel

[Jerry C.]

I think the flywheel is part number 021 but what tooth count does the starter ring have. I think 168 but could 158. Anyone know? Thanks in advance.

[Edward J.]

[Todd L.]

Re: 1963 Flywheel

Hey Jerry,

The part # is 3781021 and it is 153 tooth.

Todd

[Gary B.]

Re: 1963 Flywheel

Todd,

The casting # is 3791021 (not 3781021), and the GM part number is 3791022.

Gary

PS - When searching for one, on eBay for example, it’s good to search separately for both the part number and the casting number, since many people only mention the casting number.

[Todd L.]

Re: 1963 Flywheel

You're right Gary, that was a typing mistake on my part, 3791021

[Tom P.]

Re: 1963 Flywheel

Jerry, my 63 flywheel (10.5) has a date. Also I believe if you have a bigger flywheel (11”) the 421 bell housing will not work? Maybe someone can confirm this.

There is no such thing as a Chevrolet 10.5in flywheel.
There are ONLY 12 3/4in with 153 teeth, or, 14in with 168 teeth.
The 153 teeth flywheels use a 10.5in clutch.
The EARLY (55-62) 168 teeth flywheels had a 10in clutch (replacements are now 10.5in). The 66-later 168 teeth flywheels use an 11in clutch.

[Edward J.]

Re: 1963 Flywheel

Tom you are correct, I should have said 10.5 clutch disc. That’s what I meant.

[Joe L.]

Re: 1963 Flywheel

All Corvettes (and most other GM cars) from 1953 to 2019 used either a 153 tooth or 168 tooth flywheel or flexplate. Here's the breakdown:

1953-62 all---------------------------------168 tooth

1963-68 small block-----------------------153 tooth

1965 L-78----------------------------------153 tooth

1966-74 big block except L-88/ZL-1-----168 tooth

1967-69 L-88/ZL-1 with 4 speed---------153 tooth

1969 L-88/ZL-1 with THM-----------------168 tooth

1969-82 small block except ZR-1--------168 tooth

1970-72 ZR-1-----------------------------153 tooth

1984-96 all--------------------------------153 tooth

1997-2019 all-----------------------------168 tooth

[Philip A.]

Re: 1963 Flywheel

Heres a good question for ya's. How much did the cast iron flywheel from the factory for the 66-74 BB except L88 weigh? Anyone?

[Joe L.]

Re: 1963 Flywheel

Heres a good question for ya's. How much did the cast iron flywheel from the factory for the 66-74 BB except L88 weigh? Anyone?

[Philip A.]

Re: 1963 Flywheel

Thanks Joe. Please dont take offense...How sure are you of the weight? Reason I ask is I weighed mine on a scale and it weighed 27lbs. So I don't know if someone thru the years replaced it with another or what. I know the weight can make a huge difference in how the engine revs and launching the car and thru the gears so I want to make sure the weight is correct and what GM put on the 427 400 hp.
I am replacing the one I took off with a steel one from Ram Clutches. They have a few with different weights for diff applications.
when asking the technical rep, he states the closest they have to the stock weight is their 33lb when they also have a 25lb so now I'm needing proof of factory weight. Do you have such a document or manual that states that?
TIA!

[Joe L.]

Re: 1963 Flywheel

Thanks Joe. Please dont take offense...How sure are you of the weight? Reason I ask is I weighed mine on a scale and it weighed 27lbs. So I don't know if someone thru the years replaced it with another or what. I know the weight can make a huge difference in how the engine revs and launching the car and thru the gears so I want to make sure the weight is correct and what GM put on the 427 400 hp.
I am replacing the one I took off with a steel one from Ram Clutches. They have a few with different weights for diff applications.
when asking the technical rep, he states the closest they have to the stock weight is their 33lb when they also have a 25lb so now I'm needing proof of factory weight. Do you have such a document or manual that states that?
TIA!

Phillip-------


I actually weighed one on an accurate, beam type scale. However, I'll double check it when I get home from this trip.

Was there a GM casting number on the back of the one you weighed and, if so, what was it?

[Philip A.]

Re: 1963 Flywheel

Yes, 3973456N. I weighed mine on a beam type as well. Thanks Joe.

[Gary B.]

Re: 1963 Flywheel



EBay item #: 392226955585

Gary

[Joe L.]

Re: 1963 Flywheel

Yes, 3973456N. I weighed mine on a beam type as well. Thanks Joe.

Phillip-------


I'll be home Saturday and I can re-check it. Actually, it felt like it did weigh more than 22 pounds but that's what I thought I read off the scale. I'll confirm, though.