'65 flywheel

[Jack P.]

Re: '65 flywheel

Twan------

It sounds like you have a 55-62 style bellhousing (also used on a few passenger cars through 1963). I've never seen one of these installed on 63+ Corvette, but I guess it can be done. To use one of these, though, one also has to use a bellhousing mounted starter. The whole set-up would be very, very incorrect.

To get the car correct, you'll need a GM #3840383 or GM #3858403 bellhousing, a block-mounted starter with an aluminum starter nose (straight across bolt pattern with long and short starter bolts), a GM casting #3791021 flywheel, 10-1/2" pressure plate assembly, and 10-1/2" friction disc. All of these parts are pretty easy to get (here in the USA, anyway) EXCEPT the 3791021 flywheel. That's hard-to-find and, as far as I know, not currently available in reproduction or aftermarket replacement.

You can use a 14" flywheel and 11" clutch if you wish. Although not correct, such a set-up will perform well. Externally, it won't look much different than original PROVIDING that you use a GM #3899621 bellhousing. There's no way I'd continue using the bellhousing you apparently have on the car now. The 3899621 is not difficult to find used (here in the USA) and it's also available in reproduction.

My 66 L79 327/350 had the 3781021 flywheel. 403 bell housing. Very heavy. I put in a lighter flywheel. Big difference on acceleration of engine.

Jack

[David L.]

Re: '65 flywheel

Thanks for all the answers,
First of all Joe, It's explicable now to me now i know that my bell house i bought in the past did'nt fit because of the flywheel is 11" (i brought it back so i don't know the # of it) also my bellhouse is "i think" from a '57 because it is always been like this, i believe that earlier Corvettes used a bellhousing that was in two pieces and the lower one is missing on my Corvette (where is the # from the bellhousing located?) the date is J1657.
The flywheel does have 11(2) 9 as date.
Yes.........the previous owner of my Corvette was NOT a Corvette lover but an &*%#$

Twan
#44079
Dutch Chapter

Twan,

The "11(2) 9" date code on your 3789733 flywheel seems a bid odd. The flywheel date codes usually starts with a letter to represent the month. The date code on my 3789733 flywheel (70 Camaro SS350) is "C 20 0" or March 20, 1970. I also have an extra 3789733 flywheel with a "H 1 8" or August 1, 1968, date code.

Dave

[Clem Z.]

Re: '65 flywheel

My 66 L79 327/350 has the 3781021 flywheel. 403 bell housing. Very heavy. I put in a lighter flywheel. Big difference on acceleration of engine.

Jack

if you have a deeper rear gear the lite weight 65 corvette 396 15# flywheel will really wake up your corvettes acceleration. don't try it with a close ratio 4 speed and a 3.08 rear gear

[David L.]

Re: '65 flywheel

Dave-----


I believe that the GM casting #3789733 flywheel was also used alternately with the GM casting #3714463 for the GM PART #3758595 flywheel which was used for many 1958-65 Chevrolet applications with 14" flywheel (but NOT 58-62 Corvette 14" applications). I think the 3789733 casting was also used for some truck application flywheels of unknown part number in the 61+ period. So, whether the 3789733 in this case "started life" as a 3758595 or a 3889694 will depend on the casting date. If it's 1966 or later, it is likely a GM #3889694. If it's 1965 or earlier, then it's definitely a 3758595 or some other truck flywheel of unknown part number.

I do not know what the difference was between the 3714463 and 3789733 castings or, for that matter, what the difference was between the 3758595 and 3889694 flywheels. The 3889694 did replace the 3758595 for SERVICE so we know there's rearward compatibility. We don't know if there's forward compatibility for the 3758595 for 3889694 applications, though. Likely there is, but I don't know that.

Joe,

Here is some part number changes from Chevrolet Parts History and my vintage Chevrolet parts catalog "library":

3789731 (Casting # 3714463) replaced in Jan. 1965 by 3758595 (Casting # 3714463) which was replaced in December 1966 by 3889694 (Casting # 3789733) which in June 1971 was replaced by 3998281 (Casting # ?) which was replaced by 3988759 (Casting # ?) which was replaced by 3991469 (Casting # ?).

Dave

[Tom P.]

Re: '65 flywheel

Twan------

It sounds like you have a 55-62 style bellhousing (also used on a few passenger cars through 1963). I've never seen one of these installed on 63+ Corvette, but I guess it can be done. To use one of these, though, one also has to use a bellhousing mounted starter. The whole set-up would be very, very incorrect.

Joe,
It IS POSSIBLE to use a block mounted starter with the early style open bottom bell housings. Although, it must be the staggered bolt pattern, CAST IRON nose version.
Since block mounted starters were never factory installed with open bottom bell housings, it MAY be necessary to do some VERY MINOR t******* of the iron starter nose or the bell housing. But the bottom line is that the housing mount starter is not absolutely necessary to be used with an open bottom bell housing. UNfortunately, I discovered this AFTER I passed up a 60-62 style alum housing at a swap meet for $50 which had the lower starter bolt hole broken off!

[Jack P.]

Re: '65 flywheel

if you have a deeper rear gear the lite weight 65 corvette 396 15# flywheel will really wake up your corvettes acceleration. don't try it with a close ratio 4 speed and a 3.08 rear gear

Hi,

My 66 L79 has a M-20 and a 3.70 rear. Lots of get up and go over original 35 lb. flywheel. I was hesitant to change, but after driving it, I will never go back to old flywheel.

Jack

[Joe L.]

Re: '65 flywheel

Joe,

Here is some part number changes from Chevrolet Parts History and my vintage Chevrolet parts catalog "library":

3789731 (Casting # 3714463) replaced in Jan. 1965 by 3758595 (Casting # 3714463) which was replaced in December 1966 by 3889694 (Casting # 3789733) which in June 1971 was replaced by 3998281 (Casting # ?) which was replaced by 3988759 (Casting # ?) which was replaced by 3991469 (Casting # ?).


Dave

Dave-------


Yes, that's how it all went. However, I believe the 3789733 casting was first used for the GM #3789731 flywheel assembly although it's possible the 3714463 was alternately used. Then, the 3789733 casting was also alternately, if not exclusively, used for the 3758595 after about 1961.

Information on casting numbers found in the "part description" column of P&A catalogs is not always accurate since it tends to be "static" and often not updated. In addition, with flywheels, casting numbers are usually not also identification numbers specific to a certain finished part number since more than one finished flywheel part number may be manufactured from any given casting and more than one casting may be used for any given finished part number.

I believe the casting number of the GM #3998281, 3988759, and 3991469 flywheels was 3789733 (same as earlier) or 3973456. Other casting numbers may also have been used. If I recall correctly, one or more of the 3998281, 3988759, or 3991469 flywheels was dual-drilled for a 10-1/2" and 11" clutch but I don't know which one(s).

By the way, the GM #3998281 was discontinued from SERVICE and replaced by the 3988759 in August, 1980 and the 3988759 was discontinued in January, 1983 and replaced by the 3991469. Some of these part numbers actually "co-existed" for periods of time during the 1971 to 1983 period. There was also another part number, GM #3973453, which, strangely, was cataloged only for 1970 Corvette with LT-1 and no other application I can find. It used the 3789733 and/or 3973456 casting number. It was discontinued and replaced by the 3998281 in April, 1975.

[Joe L.]

Re: '65 flywheel

Joe,
It IS POSSIBLE to use a block mounted starter with the early style open bottom bell housings. Although, it must be the staggered bolt pattern, CAST IRON nose version.
Since block mounted starters were never factory installed with open bottom bell housings, it MAY be necessary to do some VERY MINOR t******* of the iron starter nose or the bell housing. But the bottom line is that the housing mount starter is not absolutely necessary to be used with an open bottom bell housing. UNfortunately, I discovered this AFTER I passed up a 60-62 style alum housing at a swap meet for $50 which had the lower starter bolt hole broken off!

Tom-----


Well, that's interesting information I was not aware of.

[Joe L.]

Re: '65 flywheel

if you have a deeper rear gear the lite weight 65 corvette 396 15# flywheel will really wake up your corvettes acceleration. don't try it with a close ratio 4 speed and a 3.08 rear gear

clem------


Yes, and if one wishes to use the "15 pound", 12-3/4" flywheel on any 63-68 small block originally equipped with the standard weight 12-3/4" flywheel, then one is in luck because it's still available from GM under GM #14085720 for about 200 bucks, GM list.

The standard weight, 12-3/4" flywheel is the one that's hard-to-find. I don't understand why, though. This flywheel was used for many Chevrolet applications during the 60's and not just Corvettes. So, I don't understand why it's not available in the replacement parts market.

[Tom P.]

Re: '65 flywheel

Tom-----


Well, that's interesting information I was not aware of.

Joe,
Keep in mind that the bell housing mounted starter, staggered bolt pattern ALUM nose and staggered bolt pattern IRON nose starters are ALL for the larger, 14in diameter 168 teeth flywheels. As you probalby know, you CANNOT use an alum nose, staggered bolt pattern starter with the 444/621 style housings----------------only an iron nose will fit --------------and it also fits into the starter bulge of an open bottom housing.
Additionally, all three of these starters are in the same physical location, in relationship to the flywheel.
These are the kinds of things that us NON-numbers matching, non-correct markings, non-proper combination guys have learned after 45+yrs of jacking with old Chevys so that we can get something put together which is incorrect------------but compatible!