Hey guys so I’m shopping around for a clutch for my ‘63 Impala . It’s currently a 3 speed and I’m going to be installing a 4 speed Muncie M20. This is just for a daily driver so what size clutch setup should I get? Any brand recommendations? SACHS? Thanks
Generally , you can't put anything bigger than a 10.5" in a passenger car bell housing , there are different bells & flywheels dilled for larger diameter clutches.
Centerforce is my clutch of choice. Had one In my 63 bel-air, 350, 11”, m20 Muncie, 2:73 rear gears with a 31” rear tire.
I run an 11 inch Zoom in my car. I use a cast iron 1955 Chevy bellhousing. For years I thought it was a truck piece until I ran the numbers. The truck ones are good too. You'd have to run the truck starter that bolts to the bell. With the smaller clutch, figure what you want to do with it. General cruising, going to the track, etc.
The Rock Auto cheat sheet shows 10=1/2 for a 63 327 with one 11 inch. This I have run into more than once with a friend who wanted to put a larger clutch behind a small block Chevy and found out that the car bellhousing only handled a 1-1/2 inch bellhousing and if you wanted a bigger clutch you had to swap bellhousings and in that car it might hit the transmission hump. Still I have to ask, unless you are putting a lot of extra horsepower that might call for a bigger stronger clutch why do you think you need a bigger clutch outside of Bubba factor bragging rights?
If you want an eleven inch clutch you need the "621" (or equivalent replacement) passenger car belhousing.
Does the clutch have issues now? If no issues, you just inspect when you pull the 3speed, then decide if new is needed or not. As mentioned, a driver doesn’t need an upgrade, no point in it.
If for some reason you use a truck bellhousing, be aware that the hole where the transmission slides into the bellhousing is a larger diameter than the car bellhousing and the trans will not be centered. There are bushings available to slip in place and make them work. I'd stick with what you have unless you have replaced the engine or built one with a lot more power. Before you drop a bunch of $$$ on a NAME brand clutch, I'd contact Ky Clutch and buy a rebuilt one. (502)955 9173 They are good people..........Also, you should have your flywheel refaced before putting a new clutch in.
Use the clutch bellhousing combo you already have for the 3 speed. You are changing the transmission behind it not the engine in front of it Just inspect and replace the pilot and throwout bearings while apart. Also don't be tempted with racing/Hi-perf clutches. They are too "Grabby" It takes some skill to do a hill start with a metallic lining clutch
You can not use the 3 speed bellhousing with the Muncie. The front bearing retainer hole is too small. You will need a bellhousing from a 4 speed.
Good info Here: https://www.trifive.com/threads/muncie-4-speed-transmission.246818/ https://www.trifive.com/threads/muncie-4-speed-transmission.246818/
To clarify what @SS327 posted above there are three different register diameters for first generation SBC’s. Three and four speed passenger bells were all the same, except the 1963 with the small register for the ‘63 only small diameter front bearing retainer Muncie 4spd. The small register bell is identified by the last three digits of the casting number- ‘421. Early truck bells were the same as passenger until the late’60’s (‘68?) when they went to the larger 5 1/8” register. If anyone needs the oddball ‘421 I have one.
I've run an M21 with the cast iron 55/59 Chevy truck bellhousing that is in my 48 and swapped the same transmission to an early small aluminum bellhousing. In 50 years of working `on Chevys where I had to know what fit what as far as swapping parts around went there is the 48 and later truck / 55 and later car retainer size that fits 3 speeds SM420 and Muncie and Saginaw car 4 speeds and the later larger size that fits SM465 truck 4 speeds. You can't swap a SM465 to an older bellhousing without machining the hole out but can use a spacer ring with the larger diameter truck bellhousing to run a 3 speed or car 4 speed. The "Muncie 4 speed won't fit in the 3 speed bellhousing usually comes when a guy buys a Muncie SM465 to put in his older pickup that had a 3 speed in it and finds that it won't fit.
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