The bellhousings that take the stud which screws in from within the bellhousing were used on low HP applications, such as 2BBL V8s (at least in '57 this was true).

The bellhousings that take the larger stud which screws in from the transmission side were NOT unique to Corvettes. ALL hi-perf passenger car applications also used this bellhousing (at least in '57....)

Jim

 

That's correct - I should have said the one machined for the large transmission-side-installed stud was the ONLY one used on Corvettes, and was also used on some passenger car applications. Photo below shows the 365 bellhousing with the transmission-side-installed pivot stud installed.

 

Aluminum is about three times more flexible than iron or steel. I believe the biggest problem would be bending flexibility of the housing resulting in an NVH issue for the powertrain. That's why the later housings are ribbed; makes them stiffer. (There's a joke in there somewhere.)

 

Thank you for the clarification (there's a joke there too)

 

Mike,

Guess I missed it...... Why did they do that anyway?

 

Yeah I missed it also : All knowing one(s) - Why did they do it ?

Also can the '58 & '59 owners please confirm that their cast iron bell housings DON'T have side mounts ?
I am really having a hard time with that one ?!

 

See John's picture above. Looks right to me.

 

That's exactly my point : Is that a correct '58 / '59 bellhousing ?
Because other knowledgeable folks have said that they lost the side mounts after '57 ?

And I really don't think GM moved the stud location so it was easier to replace.
When did anyone change a design to make seldom required operation easier ?? - it's probably easier to replace inside the housing anyway.

 

The basic aluminum bellhousing first appeared in 1962 for the new 4/6 cylinder Chevy II engines. The Chevy II engines also were the first to have the 154 tooth flywheel and the smaller front bearing and retainer on the manual transmission which was essentially a carryover '55-'62 Pass car design. The new 4/6 cylinder engines also used the same block/bellhousing configuration as the v-8 engines.

The balance of the 1962 Chevrolet model lineup (except 409) kept the old Blue Flame 6 cylinder as standard, the cast iron bellhousing, large flywheel and large front bearing retainer.

Starting in 1963, the "new" aluminum bellhousing was integreted into the full size carline and Corvette along with the 154 tooth flywheel, small bearing retainer and block mounted starter, across the board. In 1963, Pass car also received the new 6 cylinder engine that had a block bellhousing bolt patter like the existing V-8 so now, all bellhousings are common except 409.

In order to commonize machining operations, all these bellhousings were machined for the carryover small bearing retainer. That included Chevy II, Corvette, and Pass car, except 409.

The following model year, all those product lines switched back to the larger front bearing retainer. If my memory is correct, I think there were durability problems with the small front bearing in use behind 327 engines and the decision was made to upgrade to the former size across the board. Again, to commonize machining.

Now you know the rest of the story.

 

That's correct (that the small hole originated with the 62 Chevy II housings), and I understood that. I should have been more clear/specific and said that I did not understand why Chevy would have gone to the small bearing retainer/small hole in the housing for the other (BIGGER) engines and other Chevy cars. The smaller retainer/hole may have been just fine for Chevy IIs, but NOT for the bigger engines/cars. And as Mike already mentioned, the 63 409s DID RETAIN the larger bearing retainer/hole in the housing!
Did I say it right that time?

Tom Parsons

 

Thanks Mike Good information.

I've never taken one apart to measure/count the ball bearings in the front race, but I guess there might be (maybe) one more bearing in the 4 11/16 large bearing. Interesting!

 

In 40+yrs of rebuilding Muncies, I've seen 3 different versions of the (larger) front bearing: 8, 11, 12 ball bearings.
The bearings with 11 and 12 are commonly referred to as "max" bearings. I buy ALLLLLLLLLLL my 4sp parts from Larry Fischer of D&L Transmission and his rebuild kits always include the max front bearing.

Tom Parsons

 

Thank you Mike for a nice explanation including the rationale behind the changes

Jerry

 

It may have been simply a change in the manufacturing process.

 

That 365 casting was used through the end of '59 Corvette production, including the "wings" that were only used for rear motormounts on car and truck applications.

 

Correct, ONLY the 55-57 pass cars used those side mount provisions.
The truck bell housing was VERY similar (but NOT identical) to the car/Vette housing. The mount pads on truck housings had a single threaded hole and the second hole had a pointed locating pin. Trucks used the side mounts up until about 1970.
For you guys who need to know some minor differences in early bell housings, here is a comparrison between a pass car (Vette) and truck bell housing. Often times at swap meets I've seen inscrupulous or unknowing sellers trying to pass off a truck housing as a 55-57 (or 59 Vette) housing.




For an early Vette, a truck housing (as pictured above) would FUNCTION perfectly, but of course would not be "correct". If a person were in a bind to get their car together and a truck housing was all that was available at the time, it could be used as an interim housing until a correct one could be located.

Tom Parsons

 

Thank you John.

Was the "365" bell housing also used on '58 '59 passenger cars ?