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Course 101 on Bell housings/Flywheels with photos

142K views 80 replies 36 participants last post by  Ramrod 1 
#1 · (Edited by Moderator)
The questions on bell housings, flywheels and clutches arise here MANY times. So, I took some pictures and will attempt to explain the differences.
First, because it comes up so often, here is a picture of the truck housing and then a picture of a truck housing next to a pass car 3899621 type housing. Notice the big, extra bulge in the lower section of the truck housing. The purpose of this additional bulge in the truck housing is to accomodate a 12in clutch. You don't want or need a 12in clutch in a car.





Next, is the truck housing turned over on top of the 621 housing to show the difference in the bigger hole of the truck housing compared to the hole of a pass car housing.



The smaller 403 type housing compared to the bigger 621 type housing.



The next two pictures are the earlier open bottom housings. There were basically 3 types, 55-57 cast iron, 58-62 cast iron, and the 60-63 alum.
Notice the 55-7 style with the provision for side engine mounts. The 58-62 iron and 60-63 alum housings are virtually identical (no side mounts). The ALUM open bottom housings were used on hi-perf 348 (pass cars) and 409 engines and ALL 60-62 Vette engines. The 60 alum open bottom is a one year only housing. The difference for the 60 is that it had a smaller hole for the bearing fork than the 61-63 version. ANY of the 60-63 open bottom alum housings are worth a small fortune!!! Also, ALLLLLLLLLLL 57-63 open bottom housings were used ONLY with the big, 14in diameter 168 teeth flywheels.





The next 2 pictures are the big, 14in dia, 168 teeth and the small, 13in (actually about 12 3/4in) dia, 153 teeth flywheels and flex plates. Notice the big flex plate has added weight on one side. This came off of a SB400, which is EXternally balanced and requires a flywheel or flex plate with added weight. The smaller flex plate came from a 307 with PG.





This picture is the engine side of two big flywheels. One is neutral balance, the other is UNbalanced. Notice the added weight on the right flywheel. This is from a 454, but an UNbalanced flywheel with this extra weight is required for BOTH a 454 (and dirivatives such as 468, 496, etc) and a SB400. The 454 flywheels are fairly common to pick up at swap meets, but it is unlikely that you will ever come across a SB400 flywheel. The 454 flywheel can be used when building a SB400 because when you have a SB400 (or any engine) built, you're going to have it balanced. Right? Right! Thus, the 454 flywheel provides the needed weight for a SB400.



The last picture shows the comparison of a 444 and 621 housing. Notice that the ONLY difference between them is the thickness of that one rib at the corner. The thin rib is the 444 housing.



Last of all, look closely at ALLLLLLLLLLLLLLLL of the housings for the big flywheel. Notice the bulge for the starter nose. That bulge sticks out about 1in from the side of the housing, whereas the starter nose bulge of the 403 style housing is even with the side of the housing.
The smaller flywheels will ONLY accept a 10 1/2in clutch. The big flywheel is required for an 11in clutch. BUUUUUUUUUUUUUT, some of the early BIG flywheels only had a bolt pattern for a 10in clutch, such as 55-7 Chevys with a V8. They all had the big flywheel, but only had a bolt pattern for the 10in clutch (in the early years, clutches were 10in but now they are 10 1/2in and fit the same bolt pattern). There have been some big flywheels with dual bolt patterns for either 10 1/2in or 11in clutches. They are kind of rare.
Study carefully, take notes, there will be a test!
 
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#61 ·
Here is a 697 (464697) housing which is identical the the 621 housing EXCEPT for the oval shaped boss for the ball stud hole.


Here is a truck housing with an adapter ring and Muncie front bearing retainer.



And here is a somewhat rare 64-65 bell housing for the 409/396 engines with a 168 teeth flywheel.



Here is a comparrison between a 444 (1966) and a 621 (1967-later) housing. The ONLY difference appears to be the wider rib on the corner of the 621 housing (top).
 
#62 ·
Ok, perhaps I'm a bit late to this party, but I have a question.

Suppose I have a 400 sbc, and it does NOT have the pivot point for the bellcrank over the oil filter pad. The 621 bellhousing appears to have a pivot point machined into it.

Can I use this on my 1965 chevelle wagon?
 
#64 ·
I just had the exact same issue, the threaded hole on the 621 BH will not line up for your z bar. I have a 400 SBC and the block had the boss but it was not drilled. It wasn't too tough to do with the inner fender removed. We ground down the tap shank to accept a cheap 3/8 socket (pounded on) so we could use a long extension and ratchet for the tapping - there was not enough room for a tap handle. Now if your engine is out of the car then so much the easier.
 
#63 ·
Russel you will have to drill and tap the hole or buy the bracket that mounts to the bellhousing bolts. The hole in the bellhousing will not line up to the cross shaft on your 65. Here is a photo of a 400 sitting in a 64 and you can see the alignment needed.

 
#66 ·
I moved the pictures in Photobucket to a different album, so they don't show up in the original post, so I'm doing it over here and putting the photos back where they were.
The questions on bell housings, flywheels and clutches arise here MANY times. So, I took some pictures and will attempt to explain the differences.
First, because it comes up so often, here is a picture of the truck housing and then a picture of a truck housing next to a pass car 3899621 type housing. Notice the big, extra bulge in the lower section of the truck housing. The purpose of this additional bulge in the truck housing is to accomodate a 12in clutch. You don't want or need a 12in clutch in a car.





Next, is the truck housing turned over on top of the 621 housing to show the difference in the bigger hole of the truck housing compared to the hole of a pass car housing.



The smaller 403 type housing compared to the bigger 621 type housing.



The next two pictures are the earlier open bottom housings. There were basically 3 types, 55-57 cast iron, 58-62 cast iron, and the 60-63 alum.
Notice the 55-7 style with the provision for side engine mounts. The 58-62 iron and 60-63 alum housings are virtually identical (no side mounts). The ALUM open bottom housings were used on hi-perf 348 (pass cars) and 409 engines and ALL 60-62 Vette engines. The 60 alum open bottom is a one year only housing. The difference for the 60 is that it had a smaller hole for the bearing fork than the 61-63 version. ANY of the 60-63 open bottom alum housings are worth a small fortune!!! Also, ALLLLLLLLLLL 57-63 open bottom housings were used ONLY with the big, 14in diameter 168 teeth flywheels.





The next 2 pictures are the big, 14in dia, 168 teeth and the small, 13in (actually about 12 3/4in) dia, 153 teeth flywheels and flex plates. Notice the big flex plate has added weight on one side. This came off of a SB400, which is EXternally balanced and requires a flywheel or flex plate with added weight. The smaller flex plate came from a 307 with PG.





This picture is the engine side of two big flywheels. One is neutral balance, the other is UNbalanced. Notice the added weight on the right flywheel. This is from a 454, but an UNbalanced flywheel with this extra weight is required for BOTH a 454 (and dirivatives such as 468, 496, etc) and a SB400. The 454 flywheels are fairly common to pick up at swap meets, but it is unlikely that you will ever come across a SB400 flywheel. The 454 flywheel can be used when building a SB400 because when you have a SB400 (or any engine) built, you're going to have it balanced. Right? Right! Thus, the 454 flywheel provides the needed weight for a SB400.



The last picture shows the comparison of a 444 and 621 housing. Notice that the ONLY difference between them is the thickness of that one rib at the corner. The thin rib is the 444 housing.



Last of all, look closely at ALLLLLLLLLLLLLLLL of the housings for the big flywheel. Notice the bulge for the starter nose. That bulge sticks out about 1in from the side of the housing, whereas the starter nose bulge of the 403 style housing is even with the side of the housing.
The smaller flywheels will ONLY accept a 10 1/2in clutch. The big flywheel is required for an 11in clutch. BUUUUUUUUUUUUUT, some of the early BIG flywheels only had a bolt pattern for a 10in clutch, such as 55-7 Chevys with a V8. They all had the big flywheel, but only had a bolt pattern for the 10in clutch (in the early years, clutches were 10in but now they are 10 1/2in and fit the same bolt pattern). There have been some big flywheels with dual bolt patterns for either 10 1/2in or 11in clutches. They are kind of rare.
Study carefully, take notes, there will be a test!
 
#71 ·
Dumb question I guess but re: truck versus passenger car front bearing retainers...what's wrong with just swapping the front bearing retainers and use the whatever bellhousing you have.... I do this with saginaw 3 speeds all the time.. Have also turned the truck bearing retainer down to passenger car diameter with no issues.
 
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