Danish Corvette Guy

Im getting ready to buy a aluminium flywheel, but im not sure if my clutch is a 10.5" or a 11"
On the original flywheel still sitting in the car is a number L 588, can anyone tell me if its possible to id the size 10,5 or 11 from this number. I have a 10.5" flywheel on my hand, but will it fit ?
Its a 4 speed muncie. (how can i tell if its a M20 or M21 ?)


Thomas

ghostrider20

M-20 is the Wide Ratio, and the M-21 is the Close Ratio.

All SB used the 10.5".

I am away from my reference material, but I am pretty sure on this.

Mark

ghostrider20

There has been recent discussion on fly wheels, Aluminum fly wheels may have some issues.

Read this.

http://forums.corvetteforum.com/show...565&forum_id=4

Danish Corvette Guy

Thanks for the reply, im buying Fidanza 168 teeth aluminium flywheel. How can i tell if its a M20 or M21. Is there a number on the gearbox i can check ?

Thomas

ghostrider20

I think you could run the numbers and find out, Post them.

I think you may need the 153 tooth gear though.

There are issues with re-surfacing aluminum flywheels, as they have a steel plate riveted to the clutch surface. In any event, my concern with the Aluminum fly wheel is it getting hot and warping. It may be a misplaced concern, but the General used Steel, even with the 18 pound L-88 fly wheel for a reason.

Mark

JohnZ

If your '66 is a small-block and has the original bellhousing (3858403), the Fidanza 168-tooth flywheel (for 11" clutch, 14" overall diameter) won't fit in the bellhousing, nor will the 11" clutch. That bellhousing will only accept a 153-tooth flywheel, 12-3/4" overall diameter, for a 10.5" clutch.

No way to tell M20 vs. M21 with it in the car by looking at it; if the rpm drop when shifting from 3rd to 4th is about the same as from 1-2 and 2-3, it's an M21 - if the rpm drop from 3rd to 4th is a lot more than it is from 1-2 or 2-3, it's an M20.

Danish Corvette Guy

The bellhousing is for an 11" clutch, the starter i bought this spring is for a 168 toth flywheel i remember now.
Im taking the gearbox out this winther to put in new bearing where the tranmission Yoke goes in, so how can i tell when i have the gearbox out ?

Thomas

ghostrider20

John, is there a difference in the input shaft splines, course and fine?

If I remember when I ordered a kit for my M-21 there may have been some options for the spline count on the input shaft. If I remember mine 65 M-21 was the course or (13 count).

Mark

JohnZ

With the tranny out, put it in first gear and count the number of turns of the input shaft it takes to get one full turn of the output shaft; if it's 2-1/4, it's an M-21 - if it's 2-1/2, it's an M-21.

All Corvette M20/M21 Muncies through 1970 had 10-spline inputs and 27-spline outputs; changed to 26 and 32 in 1971.