DSR

What is the difference between a 1965 small block bellhousing and a 65 big block bellhousing? What would be the casting number on small-block bellhousing?

Thanks Dave

wmf62

I did not know that there is a difference between BB & SB bellhousings...
Bill

R66

I don't think there is a difference either. I know I have a couple of 11" bell housings and one was off of a big block. I think they are 621s. They look identical to me.

wmf62

(and there is safety in numbers, even if the number is 2...)

Bill

Powershift

How about I agree with you two ( x3) and also site the NCRS 1965 Judging Manual and the Chevrolet Parts Book as references to support this.



Larry

wmf62

(x3)
Bill

DZAUTO

THERE IS NO SUCH THING AS A "BB" AND "SB" BELL HOUSING!!!!!!!!!!!!!!!!!!!!!
(I've only pointed this about 8 bazillion times!)

Now, with that said (8 bazillion and 1 times), there are TWO different sizes of bell housings. The smaller bell housing is used with the 153 teeth flywheel, the larger housing is used with a 168 teeth flywheel. Beginning with the VERY FIRST CHEVY V8 engine in 1955, all the way up through 1985, ALLLLLLLLLLLLLLLLLLL Chevy flywheels/crankshaft flanges have the SAME bolt pattern. Thus, ANY 55-85 flywheel will bolt up to ANY Chevy V8 crankshaft!
THE SIZE OF THE FLYWHEEL IS WHAT DETERMINES THE SIZE OF THE BELL HOUSING, NOT, repeat, NOT WHETHER IT IS A BB OR SB!!!!!!!!!
So, to answer the question about bell housings used with 1965 Corvette engines (1965 passenger car/Chevelle bell housing application is different), ALLLLLLLLLLLLLLLLLLLLLLLLLLL 1965 Corvette engines (YES, including the 65 396) used the smaller 153 teeth flywheel, thus, they used the smaller 403 style bell housing.
Below is a comparison between the smaller, 403 style housing, and the larger 621 housing (introduced in 67). Notice that the larger housing has a significantly noticeable bulge for the starter nose, whereas the smaller bell housing is straight on the right side.


The smaller, 153 teeth flywheel will ONLY ACCEPT a 10 1/2in clutch.
The 11in clutch is used with the larger 168 teeth flywheel (big trucks got a 12in clutch with the same flywheel).

NOW, READ THE FOLLOWING CAREFULLY!
ALLLLLLLLLLLLLLLLL early Corvettes and passenger cars (55-62) with a V8 engine ONLY, ONLY, ONLY got the larger 168 teeth flywheel----------------BUT, they had a bolt pattern for the smaller 10in clutch (10in clutches are now replaced with 10 1/2in clutches). The smaller 153 teeth flywheel WAS NOT USED UNTIL 1963!. Thus, ALLLLLLLLLLLLLLLL 55-62 V8 engines (it didn't matter if the car had a 265-283-327-348-409 engine) came with a large bell housing. ALLLLLLLLLLLLLLLLLLLLL 55-62 bell housings were the open bottom style, 55-59 was cast iron, 60-62 was alum (for Corvettes and hi-perf 348-409 engines), as below.

Nowhere Man

Tom post like yours NEEDS to be a sticky or in a book

wmf62

the last one is COOL.... like a scattershield....

but,. I prefer the open-bottom ones for clutch inspection and other maintenance.
Bill

DSR

Thanks for the information and the great pictures. Looks like I need a small clutch bellhousing 403 for my 65 Corvette. Dave

DZAUTO

One more time, the size of the bell housing is NOT, repeat, NOT dependent on either the engine (SB or BB) nor the clutch! the size of the bell housing to be used is TOTALLY dependent on the size of the FLYWHEEL (153 or 168 teeth)!!!!!!!!!!!

R66

At the risk of someone finding out :with stupid: isn't the clutch fork the same regardless if it is a 10 1/4" (403) or 11" (621) bell housing?

wmf62

once again, it is going to depend on the size of the flywheel; but the only difference should be the starter location. fork should be the same...

Bill

DZAUTO

Correct!
And in addition (at least back to 1949), the ball stud location/geometry for the throw out bearing fork is IN THE SAME POSITION RELATIVE TO ENGAGEMENT OF THE THROW OUT BEARING!!!! REGARDLESS OF WHICH CHEVY BELL HOUSING IS USED!!!

My 51 Chevy with a 383, has a later V8 bell housing-------------------AND I USE THE BONE STOCK 51 CHEVY FORK AND THROW OUT BEARING SETUP IN A LATER MODEL BELL HOUSING with a Muncie.
This is my clutch linkage setup for the 51, which has been like this since the first V8 installation in 1967. The ONLY thing different is that I have lengthened the linkage with some links of chain.



And here is the 51 fork going into the 57 bell housing.

R66

I agree Bill, but I really never checked. i would do it tonight, but we have a wet 4th of July show right now.

Ron

R66

Thanks Bill and DZAUTO
I am guilty of doing things and learning the hard way when they didn't work. Guess that kinda makes me a Redneck or even at times a BUBBA.

jeffbant

Damn, a lot of detail and past effort went into the responses here and I appreciate the effort! However, I am still confused. I have a 67 with a 101/2 clutch. I don’t know how many teeth on the flywheel as it is currently installed in the car. The net result of my reading suggests that if the bell housing has a bulge for the starter it is a 621, which mine does. tks

Avispa

Check the starter mount bolts. If they're straight across, perpendicular to the crank, you have a 153 tooth 12 7/8 inch flywheel and the matching bell housing. Diagonal starter bolts means 168 tooth, 14 inch flywheel and matching bell housing.

I put the small flywheel, lightweight version and 10 3/8 clutch on all my BB cars.

There are some 168 tooth 14 inch flywheels that are drilled for 10 3/8 (or 10 1/2 if you prefer) clutches. Unlikely, but you might have one.