I looked at a Muncie m21 last night. It's the trans, scatter shield, pressure plate, clutch, fork and throw out, and also comes with the right shifter for my 55 sedan. We pulled the side cover off and everything looks pretty decent. At least I didn't see any obvious cracked forks or chipped teeth. I've never had a four speed before so this is new ground for me. The owner said it came off of a 454. How much of this will I be able to use on an (as yet unpurchased) small block chevy? The scattershield should fit, but what about the pressure plate? the flywheel is different due to flywheel weights, right?
HAZMAT, you should be able to use all the parts you got, as i believe 454 engines are internally balanced just like all smallblocks (with the exception of 400 and all derivitives of the 400).make sure what ratio trans you have , as the m-21 came in both close and wide gear ratios. i personally prefer a wide ratio trans for street use as you really can get the full benifit of a close ratio box for most of your day to day street driving.i am running a m-20 in my ford and am more than happy with its wide ratio gearing. good luck, mike
yeah, what he said. That's the great thing about chevy. I would make for sure that the tranny did come off a 454, because if it came off something like a 396 the flywheel may be externally balanced. best thing i can say, is just do a little homework on the block it came off of and the one you plan to use.
What mitch 36 said is not entirely correct , but it's not too far off. First things first, Muncies came in three flavors... M20- These can be identified by the letter "A" stamped on the side of the case. They have the wide ratio gear spacing which is: 2.56/ 1.91/ 1.28/ 1.00 M21- This is the close ratio box wich has a closer gear spread. These can be identified with a "B" stamped in the case. Ratios: 2.20/ 1.64/ 1.28/ 1.00 M22- This is the one everybody and their mother has, also known as the rock crusher. The M22 shares the same close gear ratios as the M21, but it incorporates straighter cut gear teath. They are not straght cut, just straighter than the other two Muncies. This can be identified by the letter "C" stamped into the case. Ratios: 2.20/ 1.64/ 1.28/ 1.00 As for the parts you received it depends what small block you are using. The only externally balanced SBC was the 400, but in about 85, when they changed to a one peice rear seal, they changed the crank shaft and the flywheel bolt pattern and all SBCs were now externally ballanced. So you need the correct weighted flywheel with the correct bolt pattern. Most likely you are using a prior to 85 SBC, but 350's used the big block sized flywheel, which is 168 tooth with an 11" clutch. 327's and smaller used the 153 tooth flywheel and the 10.5" clutch. Even so if those parts came from a 454 it should be an externally balanced 168 tooth peice, so it should not be used even if it bolts up. Everything else should work fine.
Thanks Mitch. I was a little confused because the McLeod website shows the same flywheel for almost all v8's from 265 - 427, with the exception being the 400's (as you said) and the 454. The pressure plate part numbers were different for big block and various small blocks. I really couldn't figure that out- same bellhousing, flywheel and trans.. but different pressure plate? I'm guessing the part numbers were different due to holding strength, not a difference in part fit. The trans if definately a close ratio. It had the 11 spline / single groove input shaft. My head tells me I am better off with a wide ratio, but the hoodlum in my says go with a low rear end and a close ratio trans.
I'll second what Alf says, the 454 is externally balanced, as is the 400 SBC, the other (pre-1986) small and big blocks use a neutral balance flywheel. Does the scatter shield have the "ears" to mount with the stock 55 mounts? or does the car have side engine mounts and a rear trans crossmember installed in it?
every thing will work eccept flywheel 454 and 400 are externaly bal. 396,402, 427. and all small block eccept 400 are internally balanced.
AHhhh... ok. that explains why the 454 had the different flywheel part number. I don't think the flywheel in the purchase is anything special, so I guess it's not a big deal if I don't use it.
Nope, no ears. And my 55 sedan is all stock, inline 6 and powerglide with the front/side mounts. I was figuring I would have to change to the side engine mounts and trans mount. I'm not worried about changing the mounts but I don't have a full plan yet on what I am going to do about the clutch linkage. Isn't a clutch pivot on the driver side trans mount for tri-five chevys? I figure this is a popular swap so if I cut the trans mounts off of the frame - there has got to be a replacement pivot mount of some sort, right?
the clutch linkage has a Z bar supported at one end by a bracket spot welded to the frame, and at the other end by a bracket bolted to the bellhousing (so you want a bellhousing with those mounting holes). Also you need the pedal setup. you might find this stuff either in the hamb classifieds, at a swap meet, on ebay, or from someone somewhere parting out a stick shift car. I think 55-57 chevy car parts all fit, but nothing else will.
In a nutshell, if you use a 168 tooth flywheel on your small block it'll work. But if you use the smaller 153 tooth flywheel, the pressure plate will be too big for the flywheel, but everything else will work. Unless you're on a SUPER tight budget, sell that pressure plate to somebody who is. Buy a new one, you don't know it's true history and will cost money to get resurfaced anyway. If you're buying a new flywheel and clutch set anyway, get the 168 tooth. Gives the starter a little more leverage for a high compression motor and allows a larger, stronger, longer lasting clutch. Speaking of starters, unless you have a ministarter, your stock automatic starter may interfere with the bellhousing. Happy shifting.
agian.. you know a lot more about this than I do- I thought I saw a bolt on pivot point that spans two bellhousing mounting bolts. Basically, a univerasal bolt on pivot sort of thing. From what you are saying I need to leave the driver side bellhousing mount on the frame? I guess that's no big deal but I think it effects header fitment.
The pressure plate that comes with the trans is a McLeod borg & beck unit that looks pretty decent. so, it's a big part of the purchase for me. If I can't/shouldn't use it then that scales back my desire for the whole deal.
There might be an aftermarket bracket you can bolt to the engine to replace the original design, if not you could fab something. The headers and bellhousing mounts issue is something you have to work out....if you get the "old style" headers that hang down real low you can use the original type mounts, but some of the newer design headers require you to go to engine side mounts and a rear trans crossmember.
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