Hey guys Im about to do a M21 Muncie and 12 bolt swap into my 67 Chevelle. What clutch would you guys recommend. I was thinking about a ZOOM. Also what gears should I put out back. I want a good street/strip gear. 3.55's maybe. I dont want the car to be screamin on the highway and I dont want it to be a dog on the track. And if theres anything else I should do before I throw all this stuff on the car let me know. Thanks.

Zoom-made in Korea-if it matters to you.

Centerforce dual friction is an exellent choice except for the 500 mile breakin factor. I've had good luck with Zoom clutches;But that was 15 years ago. Definately 3:55 at least with the m21 tranny.JMHO Tony

My 66 has 3.73's with the M21, perfect in my opinion. doesnt scream too bad when cruising, and is great from stoplight to stoplight

Well a friend of my dad has a set of 3.73's so ill probally get those

If you are running a stock flywheel, then don't do the dual friction. The puck side of the disc will eat a nodular iron flywheel an ruin it in short order. CFII would be a better choice for stock type flywheels.

i had over 3k miles on a stock flywheel CF DF and no issues.
i put a new one in because i went from 2pc seal to 1pc seal motor and needed new flywheel.. 2k miles later, still no issues.
5k hard miles on the dual friction with no issues

aaron

i had over 3k miles on a stock flywheel CF DF and no issues.
i put a new one in because i went from 2pc seal to 1pc seal motor and needed new flywheel.. 2k miles later, still no issues.
5k hard miles on the dual friction with no issues

aaron


Interesting.......every DF clutch I have taken out has eaten the flywheel up terribly.

my clutch/pressure plate/ and flywheel all looked brand new.

my friend had a dual friction in his 5.0 stang for over 30k miles and flywheel was like new when replaced..

maybe yours were not broken in correctly? of the disk was in backwards?

that is odd..

aaron

These were not my cars. I have an Engine/Restoration shop. They were all customers cars. I probably have done 15 or more cars over the years and taken that clutch out. Maybe they have changed the compound recently???

Interesting.......every DF clutch I have taken out has eaten the flywheel up terribly.
CF DF here and 20K miles and no problems.

Go with a set of 373's! Perfect gear!

If your runing a 327 like in your sig then with maybe 25.5-26" tall tires & m21 i would rec 3.42 gear or 3.55 tops so you will still have decent 1/4 mle perf and somewaht resonable cruise rpm too,if your running slightly taller tires then go with 355's for sure.

But if you like/want 3k+ cruise rpm @ 60mph are are running 25.5-26" tires then go for 3.73's. But i bet after a while you will get tired of the higher open road cruise rpm along with the additional engine noise,increased fuel use etc you will have with the 3.73's if your on the open road fairly often.

But if its a high strung 327 with a healty cam twisitng to 6,500-6,800+ rpm that will see approx 50/50 street /strip duty then i guess you should likely go with 3.73 gear and just dont cruise over 60-65mph tops if running shorter 25.5-26" tires,taller tires are a different story that would allow for a slightly more reasonable cruise rpm at 60-65mph speeds.

Suggestion,since you say your friends father is runing 3.73's in his car so if both of you have the same approx tire hight for an apples to apples compairison why dont you ask him to take you out on the open road so you can experience the cruise rpms at like 60-65-70mph with 3.73 gear so you see /experience it for yourself.

Then you can see for yourself what the 3.73's are all about on the open road before installing them but make sure to measure your tire height and his tire height prior to the test so you know to add or delete a few rpm to match what rpm your tire size would have @ cruise with 3.73's if they are not the same approx height to begin with.

For ex,25.5" vs 26" tires would be no big deal but if you have 25.5" and your friends father has 27.5"-28" tires that would be a considerable difference which is why i am mentioning it.

But in summary if it were mine with a mild to moderate lvl perf 327 that will see considerably more open road cruising then strip use the "best comprimise " with approx 25.5-26" tires would be 3.42 gear & with taller tires like 27.5-28" it would be 3.55's .

But not 3.73's unless it's a pretty darn hot 327 turning high rpms on top end with less trq in lower to mid range rpms and you want to be reasonably competitive at the strip .

Scott

I hate to be the bearer of bad news, but you can't do it with a 4 speed without some compromise. 4.56 or 4.88 is a great track gear, but it sucks on the street. 3.08 is great for cruising the highway at reasonable rpm, but lousy off the line. 3.55 is kinda ok at either , but good at neither.

I've run 2.73, 3.23, 3.55, 4.10 and 4.56 gears in my car over the years. Each is better suited to a certain application.

Now, with BB torque, I'd go with a nice wide ratio 5 speed trans sith about .80 overdrive. The old school M21 and M22 are great with a 302 that has no torque and very peaky HP, but lousy for today's BB with a good cam.

Devin