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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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#31 ·
Tom,
excellent information. Nice work.

Would you happen to have the lowdown on clutch forks. What fits what?
I'm wondering just how many are the same and fit different applications/years.

Another good topic might be illustrations on how to index your bellhousing. I know how it's done, but I'm sure many have never even heard of it. It may solve some vibration issues for somebody??

As a side note, I too have seen these 12" truck bells on eBay and the crooks who are trying to find suckers to buy them. I'm starting to see more of them at swap meets also.
Nate
 
#33 ·
As you mentioned, the ChevyII/Nova housings fit ONLY the small flywheel. They have the same shape as a "regular" small housing, with the MAJOR difference being the lower position of the fork hole.
I realize that many people are not extremely familiar with the various bell housings, but once you see a ChevyII housing (its like seeing your first rattlesnake), there will be no mistake in the future! Or, like seeing the truck housing as pictured at the very top here. You can't mistake a truck housing and you can't mistake a ChevyII housing! :D
 
G
#34 ·
And to hopefully add more useful info about the adadpter ring for using the truck b/h in a car application, I saved this!

"However, GM cast literally millions of the 460 486 bellhousing to cover the larger flywheel and clutch in 1970's light trucks, both 6 and 8 cylinder. The problem is the Muncie SM 465 truck transmissions had a 5 1/8" (5.125") front bearing retainer, so you can't use it with the smaller car transmissions.

Luckily, a 4 11/16" x 5 1/8" bushing is available from Novak part # BR-4 (about $40) at;

http://www.novak-adapt.com

or 877-602-1500. His user name is: dennymac

I bought one of the adapter rings, and used the truck bellhousing, which cost $25 at my local salvage yard, where they use the truck bellhousings for door stops.

The 486 dust cover is GM part #340 254."

pdq67

Best Car Insurance | Auto Protection Today | FREE Trade-In Quote
 
#36 · (Edited)
Dale,
Go back to the TOP of the FIRST page. Look at the LAST photo I posted. It is a comparison of the 3899621 and 3872444 housings showing the ONLY difference is that one rib at the corner of the housing. Otherwise, these two housings are identical in every way except for the casting numbers. The 444 housing was used in 1966, and probably used some in 1967, mostly on BBs. The Vette guys go crazy for this housing for their 66 427 Vettes. There have been a few of the guys here who say their original 66 BB Chevelles also have a 444 housing. Functionally, it doesn't matter which housing is used, the only difference is that rib and the casting number.
It just so happens that amoung the bell housings that I have, one of them is a 444 (the one pictured). I came across it in a swap meet a few years ago for about $50 as I recall. The Vette guys are paying $250-350 for them. There is no way I would buy one today for that amount!!!!
 
#38 ·
Dirk,
That translates to Jun 16, 1961. (the casting number is covered up by the Muncie)
That style bell housing (with some MINOR variations) was used through 62 on pass cars and until about 1970 on some trucks. The pan and the front cover (3934908) are still available from GM.
This type bell housing used a starter that was attached directly to the bell housing (NOT the bottom of the block) with 3 bolts. But, on later blocks that have the starter bolted to the bottom of the block, you can use a starter with a CAST IRON nose and staggered bolt pattern with this housing. These housings were ONLY used with the 14in, 168 tooth flywheel that used an 11in clutch.
 
#41 ·
Hey Tom
This is dirk again i checked with the GM dealer here in Canada and was told this part 3934908 was not available. What years should i look for at the scrap yards and swap meets. Does it have to be for a BB block. Which cars or truck would be the same Thanks Dirkey
 
#42 ·
Hey Tom
This is dirk again i checked with the GM dealer here in Canada and was told this part 3934908 was not available. What years should i look for at the scrap yards and swap meets. Does it have to be for a BB block. Which cars or truck would be the same Thanks Dirkey
Dirk,
I said it was still available because I went to the gmpartsdirect web site and it still showed to be good (thus, it should be!!!!!). I'll check them again.
BUUUUUUUUUUUUUUUUT, regardless, here is what you need. ANY 55-62 pass car, and ANY truck (such as 1/2ton pickup) up through about 70 that still used the OPEN BOTTOM style bell housing, also will have the same lower pan and the flat front cover.
It DOES NOT matter if it is a BB, SB or W-motor, the bell housing and related parts are totally independant of the engine (of course this style housing was never used from the factory on a BB--------------------BUT IT ALL STILL BOLTS TOGETHER!!!!!).
The backside of ALLLLLLLLLLLLLLL Chevy V8 engines, all the way back to the very first 265 in 1955, have the same bolt pattern and they all fit over the same size 168 tooth flywheel.
 
#43 ·
Well, I either transposed a number in the part number, or, it has become discontinued since Fri.
I just called my parts guy at the Chev dealer and he says it is not a good number, so I must have transposed a number. I have two brand new ones at home. As soon as I get home, I'll check the part number on them and see what the deal is.
 
#44 ·
Tom I have a few questions on some bellhousings that I bought for $5.00 each. (I bought them to get a 621 that I needed.)

I have two 3840383 and one 3858403 these a re 10½" clutches right?

I have a 6270026. Was this a Vega B/H? Does it have any use other than a Vega?

The last one is a 409 truck steel bellhousing 3815891. Was it used on anything besides the large truck with a 12" clutch?

In your opening statement, you discounted the use of a 12" clutch. I have a new centerforce 12" dual friction that I was going to put between my built 409 and my M-22, simply because I have them. I also have a new McLeod scattershield. Do you know what fork I can use?

Thanks,
 
#47 ·
Tom I have a few questions on some bellhousings that I bought for $5.00 each. (I bought them to get a 621 that I needed.)

I have two 3840383 and one 3858403 these a re 10½" clutches right?

I have a 6270026. Was this a Vega B/H? Does it have any use other than a Vega?

The last one is a 409 truck steel bellhousing 3815891. Was it used on anything besides the large truck with a 12" clutch?

In your opening statement, you discounted the use of a 12" clutch. I have a new centerforce 12" dual friction that I was going to put between my built 409 and my M-22, simply because I have them. I also have a new McLeod scattershield. Do you know what fork I can use?

Thanks,
The 383 and 403 are the "small" housings. They will ONLY work with a 13in (actually about 12 3/4in) flywheel and the 13in flywheel will ONLY accept a 10 1/2in clutch. The 383 is the earlier version of this style housing. Frequently, the Vette guys are willing to pay good money for a 383 housing. Even though I'm somewhat familiar with the numbers on parts, I AM NOT a numbers person! I'm only familiar with the numbers for the specific purpose of determining what will fit and what is compatable with other parts.
FROM THE FACTORY, the 12in clutches were ONLY used on trucks (with the 14in flywheel and the bell housing with that extra bulge on the bottom). I've never used an aftermarket 12in clutch with a 621 style housing. If you have one, and it will fit in the 621 housing, then that would be fine. As far as I know, a stock pass car type clutch fork will also work with the 12in clutch.
The 026 housing (Vega) that you referred to, does that have the hole for the clutch fork at a lower angle than the pass car housings? If so, that was also used on the early ChevyII.
The full enclosure alum housings that I am familiar with which were used on trucks will have a hole that is too big for car trannys (such as a Muncie). Check the hole in the truck housings, if it measures 5 1/8in, the hole is too big. The hole in a housing for a car should be 4 5/8in.
Now, there is one last exception. The 421 housing. It will have a hole that is 4 3/16-----------------------THAT IS A 63 ONLY HOUSING-----------you don't want one of those, they're only good for a factory correct restoration on a 63 car (full size or Vette).
Hope this helps.
 
#46 ·
How about 3734908 for the front cover!!!
And 3704923 for the pan under the bell housing (BOTH still show to be good from Chev parts dept).
 
#51 · (Edited)
Dan,
The SB400 and 454 flywheels are different because they have different weights. A 400 manual flywheel is super rare, the 454 flywheel is fairly common. Over the years, I have picked up several 454 flywheels at swap meets for $25-50. When I build a SB400 (for a manual tranny) I always use one of the 454 flywheels. The reason is because when building ANY engine, it is going to be balanced (YOU DO HAVE YOR ENGINES BALANCED, RIGHT?), thus, the 454 flywheel has the added weight needed so my machinist just balances the flywheel as needed for the 400.
There is a down side for this. SUPPOSEDLY, 400 and 454 flywheels are ALL balanced (actually, UNbalanced) equally. Therefore, if and when a 400 or 454 flywheel (or flexplate for an auto tranny) needs to be replaced, the new flywheel will be a direct replacement because they are all SUPPOSED to have the same balance (or UNbalance). So, when a 454 flywheel is used to balance a 400, some metal may be removed, thus changing the UNbalance of that particular flywheel, and as a result, that particular flywheel is now uniquely balanced for just that specific engine. So, if you ever needed to replace that particular flywheel, you would need to remove it first, take it and another 454 flywheel to a machine shop that did balancing and have the new or replacement flywheel balanced to match the old one.
BUT, think about it, just how often does a flywheel have to be replaced because it has gone bad?????????????? Consequently, I go ahead and use the 454 flywheel for balancing a 400 and never worry about it. So far, so good.

OH ya, what's the casting number of the flywheel that you have?
 
#53 ·
That's a 454 flywheel (3973457N).
The L98 translates to Nov 9, 78 (or 88). No 454s built in 68 and if it were 98, then the bolt pattern wouldn't fit your crank. I'd say the higher probability is that it is a Nov 9, 78 flywheel.
 
#58 · (Edited)
All,

I can't view pictures either. It doesn't make any difference if I am logged in or not. I checked my profile and display pictures is already turned on. Any other ideas for me to check?
thanks

Can someone also send me PM so I can see the pictures? This is a super post and I would like to get the pictures to go along with the text?

thanks
 
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