Re: Differences between 621-444-697 housings
Tom-----
Yes, I was aware of the difference between the '444' and the '621' bellhousings that you described. As far as I can tell, it's the only difference. I've also speculated before, as you've done, that the change was made to accomodate some chassis requirement. Certainly not a Corvette requirement, but, possibly, Chevy II or Camaro.
I was not aware of the difference between the '621' and the '497'. I'll check this feature out since I have NOS examples of both the '621' and '497' castings [none for sale]. That is a feature that I don't think that I checked before, since I was mainly concentrating on external differences. I'd guess that sort of a change was done in order to remedy a cracking problem at that location with the '621' casting. I wasn't aware of suce a problem, but I'm sure that GM wouldn't have made such a change unless there was such a problem.
The 409 bellhousing that you refer to was used for 1964 Chevrolets with 409 and early 1965 Chevrolets with 409. It MAY also have been used on later 1965 Chevrolets with 396. I'd forgotten about that one. It's a "full-round" aluminum bellhousing, but it's a SAND CASTING, like 60-62 Corvette and other Chevrolet aluminum bellhousings, and not the permanent mold or die casting like the later aluminum bellhousings. It was GM #3843941 (cast 3843942) and, later, GM #3866982. Both of these are quite rare pieces, indeed.
Tom-----
Yes, I was aware of the difference between the '444' and the '621' bellhousings that you described. As far as I can tell, it's the only difference. I've also speculated before, as you've done, that the change was made to accomodate some chassis requirement. Certainly not a Corvette requirement, but, possibly, Chevy II or Camaro.
I was not aware of the difference between the '621' and the '497'. I'll check this feature out since I have NOS examples of both the '621' and '497' castings [none for sale]. That is a feature that I don't think that I checked before, since I was mainly concentrating on external differences. I'd guess that sort of a change was done in order to remedy a cracking problem at that location with the '621' casting. I wasn't aware of suce a problem, but I'm sure that GM wouldn't have made such a change unless there was such a problem.
The 409 bellhousing that you refer to was used for 1964 Chevrolets with 409 and early 1965 Chevrolets with 409. It MAY also have been used on later 1965 Chevrolets with 396. I'd forgotten about that one. It's a "full-round" aluminum bellhousing, but it's a SAND CASTING, like 60-62 Corvette and other Chevrolet aluminum bellhousings, and not the permanent mold or die casting like the later aluminum bellhousings. It was GM #3843941 (cast 3843942) and, later, GM #3866982. Both of these are quite rare pieces, indeed.
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