Hey everyone,
I am trying to convert my 68 Elky to manual. Right now I have a ZZ4 350 with long headers and a Th400 trans. Im planning on getting putting in a M20 manual, a centerforce clutch, and a hurst shift kit. Will this work? Will I need to move the trans mount? Will the long headers get in the way of the clutch and shifter? I thought the M20's came stock so I was planning on hopefully bolting it in. Thanks for any help, I really appreciate it.
David

Dave

Not sure I can answer your questions, but I have a zz4 in a 67 with a M21. I believe before you select your tranny you need to know what the rear gear is. M20's seems to work better with 3:43 and 3:55 gears. A M21 or M22 work better with a 3:73 or 4:10 rear. Also need to consider your tire height. I run 4:10's in my 67 and think maybe 3:73 would be better.

Hey Thanks for the info. Im not sure what rear end I have but it seems almost like a freeway rear end. Are you runnig long headers with your ZZ4? Is the bellhousing getting in the way at all? Thanks for your help.
David

For street use, the lower 1st gear of the M20 is probably a better choice. The gear spreads are the same as the M21 except for 3-4. If you've got some racing (drag or road track) in your plans the M21's ratios might be a better choice (combined with a lower rear gear). As far as header clearance goes, the manual should pose no problems.

For street use, the lower 1st gear of the M20 is probably a better choice. The gear spreads are the same as the M21 except for 3-4.


I'd agree with the M20 being a good choice for a street car. I have run thse w/ 4.46 & 4.11 rear gears and would would go down to even 3.31. The M20 has a 1.52 1st gear whereas M21/M22 have a 2.2 first gear. It's the lower aer that is different, not the 3-4. All have a 1/1 4th gear ratio for final drive. However, If I had the option I would rather have a ST10 with a 2.88 first gear. This lower 1st gear is great for the street. With a M21/M22 trans with a 2.2 1st gear you will nedd a fairly steep axle gear ration to get an equivalent overall 1st gear to take off with. For a little more bucks I would rather have a 5-speed. Kepp in mind most of the later cars have killer 1st gear ratios OVER 3.0+ which gives them excellent take off (e.g., mustangs). A 2.2 1st gear is comparable to a approximaelt a 3rd gear is a 5 speed. How quick would would one of those 5.0 mustangs be if it took off in 3rd gear? Go for the lowest ratio (high number) 1st gear you budget permits.

David

I run Hedman Hedders, the ceramic coated ones. No problems at all. Clutch spring may have to be relocated.

The actual percentage drop between 1/2 and 2/3 between the M20 (wide ratio) and M21 (close ratio) is about the same; not enough for all but the most sensitive 'seat-of-the-pants' driver. It's the 3/4 percentage that makes the M21 more desireable for racing applications. For a heavier car with a high rear gear ratio (3.07 to say 3.73) the M20 does offer a bit more low end response.

1/2 - M20 25.39% vs M21 25.45%
2/3 - M20 22.34% vs M21 21.95%
3/4 - M20 31.51% vs M21 21.88%

If you can find a 63-65 M20, the gear ratios are a little different but not much.
1st gear is 2.56 vs 2.52,
2nd gear is 1.91 vs 1.88,
3rd gear is 1.48 vs 1.46.

The really big difference is reverse between the M20 and M21/M22. The M20 has a 3.11 (3.16 early model) reverse vs. the 2.27 of the M21/M22. Makes backing up with a higher gear easier as well.

Hey thanks for your help everyone. I think I'll go with the M20 then. Thanks again for all the advice its really hard to find sometimes.
Thanks
David