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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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#4 ·
Great job Tom, now I'm wondering if you have a list of cast numbers for pass applications (non-truck) that accept the 11 inch clutch. That would be most useful. FYI, I'm sure by now everyone knows that the 444 and 621 bells work but they also cost a fortune; I personally always forget the one which supercedes the 621. Jason.
 
#5 ·
Ted,
At one time I always passed up the truck bell housings at the swap meets (they could always be picked up for $10-25) because I considered them useless. BUUUUUUUUUUUUUUUT, now I'm having serious second thoughts because there are now spacer rings available (someone right here also makes them) to allow a pass car tranny, such as a Muncie, to be adapted to the truck housing. So, if you see a truck housing at the swap meet for cheap, it may now be worth buying. I think I'm going to start picking them up if they are cheap enough.

One thing that I left out is that all 3 styles of bell housings (403, 621, truck) require a different stamped sheet metal cover which goes in front of the lower portion of the housing. ALLLLLLLLL 3 are still available from Chev parts dept. I just picked up one for that truck housing yesterday (my cost was about $15).
 
#8 ·
One thing that I left out is that all 3 styles of bell housings (403, 621, truck) require a different stamped sheet metal cover which goes in front of the lower portion of the housing. ALLLLLLLLL 3 are still available from Chev parts dept. I just picked up one for that truck housing yesterday (my cost was about $15).
And isn't it amazing that people sell them on ebay for quite a bit more than that and have the audacity to list them as NOS:clonk: Thanks again Tom for your effort as I'm sure it is appreciated by all!
 
#6 ·
Excellent job Tom and much appreciated:hurray: Now all the info is in one place. Maybe it would be worthwhile putting it in the Tech Section so folks don't always have to search the forums?????????????:beers:
 
#10 ·
Tom, one interesting note...the cast iron housing with provisions for side mounts looks exactly like the original bellhousing to my 64 C10 with 6cyl and 3-speed Saginaw. When I converted this truck to a 1969 vintage 350 V8, not only did the 6-cyl flywheel and bellhousing work just fine on the 350, but so did the starter, which mounts to the bellhousing, NOT the engine block. This could be useful information to engine swappers.
 
#12 ·
Tom
Great job, But I have a question. When I got my 67 BB it had a open bottom aluminum housing with the 621 number on it. I assumed the bottom had been cut off, was it? or is it for real. Also what did they use for a cover on the bottom?
 
#13 ·
Mike,
You are EXACTLY 100% correct!!!!!!!!
A bell housing, SIMILAR to but not the same as the 55-7 car housing, was in fact used on trucks from 55 until about 70. Maybe I should have gotten into some detail about that particular housing but I was trying to stay as close to car related as possible (with this being a Chevelle site). I specifically included that full enclosure alum truck housing because that housing is frequently sold by unscrupulous people as a "BB" housing to guys who need the big housing (621 type). My intention was to educate those who don't realize that the truck housing is NOT a car or "BB" specific housing.
So, now that you have bought up this issue, let me include some information about the "EARLY" truck housing with side mounts. As you can see from the above pictures, the 55-7 Chevy pass cars used a housing with side mounts (there were two mounts on the front of the of 55-7 V8s, thus, in my opinion, providing the BEST engine mounting ever for a Chevy V8). The trucks (55-70) also had a SIMILAR bell housing with side mounts. BUT, for mounting purposes, the early truck housing WILL NOT work in a 55-7 Chevy. The reason is because the truck housing has ONE threaded hole and one pointed pin for proper psoitioning of the mount that attaches to each side of the housing. ALSO, THE FLAT SURFACE ON THE TRUCK HOUSING FOR THE MOUNT IS AT A COMPLETELY DIFFERENT ANGLE THAN THE THE FLAT SURFACE OF A 55-7 CAR HOUSING! So you can't use the early truck housing on a 55-7 Chevy. ALTHOUGH, as far as using the early truck housing for just the bell housing function, it works just fine.
Last, Mike you're also correct that the bell housing/flywheel which you mentioned would fit a V8 as well as the housing mounted starter. In 1963, the Chevy 6cyl engine was TOTALLY redesigned and the back of 6cyl blocks was changed to be the same as all V8 blocks. Thus, starting with 1963 6cyl engines, the flywheel, starter and bell housing are totally interchangeable with V8s. When the 6cyl engines stopped using the "early" style cast iron housings (about 70-71) and switched over to the full enclosure alum housings, they also started using both the small and big flywheel/housing. GENERALLY speaking, the smaller, lighter duty pickups got the small flywheel/housing and the heavier duty pickups or trucks with a 6cyl got the big flywheel housing. FOR THE MOST PART, THE PICKUPS WITH THE BIG FLYWHEEL/HOUSING ALSO HAD THE SAME HOUSING AS THE CARS. The trucks with the "truck" housing as pictured above, were usually big trucks, such as 1ton and bigger, that had a 5sp (or more) tranny and 12in clutch. Sorry I didn't add this info also.

And now that we've gone through all of this, let me add one more thing.
That housing with side mounts for 55-7 Chevy cars was also used on the 55-7 Vettes, BUT, the Vettes DID NOT have mounts on the bell housing. The Vettes started out in the very beginning (53) using a rear mount on the tranny tail housing, thus, even though they used that same bell housing with mounts that was used on 55-7 cars, they didn't use the mounts on the housing (at the time, there was only ONE style V8 housing). In 58, everything (except trucks) went to a tranny mount, so the side mounts on the housing also went away in 58.
 
#15 ·
Joe,
A 621 housing was a FULL ENCLOSURE housing. If it is now an open bottom, then someone cut it off!!!!!!!!!!!!!
For the genuine open bottom housings (iron or alum) a stamped sheetmetal pan (same pan) was used. Also, there was another sheetmetal cover that went in front of the housing.
The full enclosure type housings only had the cover on the front of the housing, and those are still available from Chev parts dept.
 
#17 · (Edited)
Jody,
The ChevyIIs/Novas didn't get a V8 (from the factory) until the 64 model. The 62 ChevyII got the totally new design 6cyl engine (introduced in 63 in all other Chevys) which had the same exact bolt pattern for a bell housing as the V8s. The 63-later 6cyl also had the same crankshaft bolt pattern for the flywheel, thus, 63-later 6cyl and ALLLLLLLLLLLLLLL V8s shared flywheels/bell housings.
As you mentioned, the early ChevyIIs/Novas had the hole in the bell housing for the bearing fork positioned at a lower angle (this was unique only to early Novas). The Nova flywheel/housing will still bolt up to ANY V8 engine, thus, engine swapping is easy. To the best of my knowledge, the last year for the "offset" fork hole in Nova housings was 1967. In 68, with the new design ChevyII/Nova, they got the "regular" bell housing.
Also, all of the early Nova flywheels/housings were the small version (63-67). None of the early Novas got the big flywheel/housing, nor, have I ever seen a big housing with an offset fork hole. But, what I have seen, are bell housings with a right hand fork hole for right hand drive cars!
As you know, a BB option in a ChevyII was first available in 68 (the new design body). In all these years, it has NEVER occured to me to look and see if a BB Nova had the small or big housing/flywheel. Although, I'm sure that FACTORY BB Novas got the big one. As far as I know, only a VERY FEW BB Vettes got the small flywheel/housing, all other BB cars only got the big versions. And while we're on the subject, the SB400 ONLY came with a big flywheel/bell housing or flexplate.
I don't have, and have never had a need for the Nova housing with the offset hole, thus, no pictures. Over the years, I've passed up several at swap meets, and they were fairly cheap. Probably should have picked up one or two.
For those who don't know about the Nova housing, as Jody mentioned, the hole for the bearing fork was offset lower down, at about the 7o'clock position. The reason for this hole offset was for clearance of the clutch linkage. This type housing is unique ONLY to the 63-7 Novas (I really don't know what kind of a housing was used on the 62 Novas since they had the "old" design 6cyl). Another thing that was unique ONLY to early Novas, speifically for clutch linkage clearance, was the oil filter pad on the engine. The Nova V8 engines had the filter pad recessed about 1in deeper up into the block so that there was more clearance for the oil filter. These unique blocks were ONLY 283 and 327 engines. They are a somewhat rare block------------------BUT NOT PARTICULARLY DESIREABLE. Thus, if you run across one, it won't particularly have a very high value for the 283 and a little higher value for a GOOD, rebuildable 327 block that hasn't been bored excessively. A std bore Nova 327 will have the highest value, a .030 bore a little less value and a .040 or .060 bore will not have much value.
 
#18 ·
I can fill in some of the blanks on Nova Bells....

Casting # ending in '383' was used in 62-63. This had the fork at 7 o' clock, and a small hole for the bearing retainer - too small to use a "normal" muncie / T10, etc.

Casting # ending in '309' was used from 64-67 in ALL applications. This had the fork at 7 'o clock, and a "normal" size pilot hole for a Muncie bearing retainer. This is the one you want to use if you are building a 62-67 Chevy II V8 car. I have heard of people maching the '383' housing pilot larger, but it seems like more trouble than it's worth, IMO.


All 62-67 Nova bells were for 153 tooth flywheel / 10.4" clutch.

'68-up Novas used "normal" Bellhousings, with the fork at 9 'o clock, just like Chevelles.

Hope this helps. :)
 
#19 ·
The 62 used the old 62-earlier design 6cyl and then the 63-later got the totally new design 6cyl engine which had the same exact bolt pattern for a bell housing as the V8s (62-older Chevy 6cyl engines used a totally different bell housing from V8s-----------NOT interchangeable).
Tom... this is correct for Full size Chevy's, but NOT for Chevy IIs. The '62 Chevy II had the "new style" 194 ci engine. Chevy II NEVER used the "old style" 235ci Blue flame six.

Read my post above for semi-detailed descriptions of CII bells. '64-67 '309' is the only one you want for what most of us would build.
 
#21 · (Edited)
There MAY be some aftermarket 12in clutches that will in fact fit into a "regular" big bell housing (621 type). But the normal 12in clutch pressure plate used in big Chevy trucks won't clear the 621 type housing. That's why the trucks had that extra bulge in the bottom of the housing. If you have a 12in clutch that clears a 621 type housing, then it must be fairly narrow around the outer edge.

Novadude,
Thanks for the clarification and additional information!
If the 62 ChevyIIs got the "new" design 6 in them, then I wonder why everything else got the old 235 rather than waiting until 63 to get the new 6?
 
#23 ·
There MAY be some aftermarket 12in clutches that will in fact fit into a "regular" big bell housing (621 type). But the normal 12in clutch pressure plate used in big Chevy trucks won't clear the 621 type housing. That's why the trucks had that extra bulge in the bottom of the housing. If you have a 12in clutch that clears a 621 type housing, then it must be fairly narrow around the outer edge.
Tom - I have the McLeod 12". The PP is notched where the bolts attach it to the flywheel, that's probably how they make it fit.
 
#22 ·
Im suppose to pick up a CII bell housing later this week if it comes through maybe I can email a picture to someone and they can post a picture. Jim
 
#24 ·
I, too, have a '309' Nova bell in the garage waiting for my 4-spd conversion project ('65 Nova). If anyone needs pics, PM me.

Tom - the "new style" six in the '62 Novas was 194 ci, while the '63 Full size cars got the 230 ci engine. Maybe the 230 ci stuff was not ready in '62? Just a guess...
 
#26 ·
Jody,
To the best of my knowledge, the ChevyII/Nova housing is unique ONLY to the 62-67 cars, nothing else.
 
#27 ·
Jody,

The Vega/Monza cars used a lower mounted fork but they were cable operated and used a fork with the ball stud on the passenger side of the bellhousing. The thirdgen Camaro/Firebird housings have the fork at about 8 o'clock but they have a bracket for the slave cylinder cast on the side of the housing. Probably not what you were looking for though.

Regards,
Gary Anderson
 
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