skryla

Any war stories will be appreciated. I am anticipating 95% street, 5% (or less) strip use.

If so, what gears should I put in my 8.5 10 bolt?

jensenracing77

i would be less worried about holding up to the HP as i would be the torque. what kind of torque are you producing?

skryla

engine is not built yet but I am planning for about 550tq

MN71W30

IMHO It'll be fine. I used them for decades and only blew up one and it broke as I was backing out the driveway.
I would determine if it is a close or wide ratio first. If it has one ring groove in the input shaft it is a close ratio. 2 rings wide ratio. I prefer the 2 rings wide ratio because it has a 2.52 first gear instead of a 2.20 close. If it is a wide I would opt for 3.42 gears because you can still leave the line at the track but it is pretty hard on the clutch. If it is a close ratio, plan on first gear being over 10% longer and burning the pressure plate a little more. Either way it will be fine.

MN71W30

Sticky tires with no mercy hole shots = broken 4 speeds

skryla

I thought only the M20's had wide ratio's?

compedgemarine

M20 is wide ratio
M21 is close ratio
M22 is close ratio with straight cut gears and is stronger.
any would hold up but as was said "sticky tires" will break it sooner or later. I too have beaten the crap out of some and they lived. go through it first as any little issue will cause a big problem later.

jensenracing77

if the teeth are still thick and has not hat the snot beat out of it i think you would be OK. i would not run a set of slicks and dump the clutch with it but would be ok for the street. the W-30 had what? 500 tq, didn't the W-30 only have the M-21 in it. i am not sure about that? i broke an M-21 but it was from wheel hopping.

compedgemarine

years ago I had a 76 trans am with a M21 in it. it had a 13:1 400 and I ran it on the street with open headers and slicks. I would routinely launch it at 5000rpm and it never did break. I kept waiting for a rod to come out so I sold it before I could break it but the next owner ran it for a while before I lost track of it. as was said if the teeth are good and everything is in tolorance then what do you have to lose?

skryla

I can get an M21 fully rebuilt (never in car) with all conversion parts excluding pedals and z bar for $700. Should I do this or save my money, drive the auto for another year and get a 5 speed setup next year?

MN71W30

Good question,
I pulled our M20 out of our Olds and installed a 5 speed and it was the best swap I've ever done. Primarily because the car will be used at the track and the highway. With a 4 speed you usually need to gear the car to get out of the hole at the track. We had a 3.42 posi with a wide ratio Muncie. It is a decent combo but 70 mph seems too rev the motor a little too high for me and the launches burned up the pressure plate and the clutch wouldn't hold sometimes.
You probably know all this but in case you don't yet, the 5 speed Richmond has a 3.27 first gear and a 1-1 5th. We changed our 3.42 to a 3.08 that dropped the tach over 10% down the highway and it comes out of the hole like you got a set of 4.10 gears. I would consider 2.73 gears with a 5 speed. I had a 5 speed apart and the gears look to be straighter cut like an M22. In fact some of the parts seem to interchange like the shifting collars. I haven't confirmed this yet. Do your homework!JMHO

jensenracing77

i have seen rebuilt M-21s go for more than that alone. i would not buy one if they would not let me take the side cover off of it. i have seen people put bad guts in one with new bearings and called it rebuilt. i also seen people but M-20 guts in a M-21 and tries to sell it as a M-21.

skryla

If you don't mind me asking, how much should 5 speed conversion cost me? I might buy the M21 setup, sell it off and keep the accessories (bell housing, flysheel, clutch, pressureplate, driveshaft)

MN71W30

I definatly agree with Jensenracing77 about the price and the possible problems, it seems fair if it is good stuff. I just sold a nice M20 Muncie last week to a friend for $450 without a shifter. The 5 speeds aren't cheap and seem to hold their value better than Muncies. I found a used one for $800 a few weeks back in AZ but usually their over $1000. The shifters are expensive too. They cost $450 new and used ones are about half that. I would buy the 4 speed and run that until I found a good deal on a 5 speed with a shifter or just leave the 4 speed in there. I bought my Richmond 5 speed from racingjunk.com for $1700 with the shifter. It was all brand new and never used. I paid more knowing it was new for reasons stated earlier about kobbled together trannys. My Doug Nash I got off craigs list for $300 but it needed a bearing and a gear bushing. The guy did say something was wrong with it. You cannot look inside a 5 speed like a Muncie or BW St-10.
What gears do you have in the rear?

skryla

I am still planning out the car so I only do it once. I don't have the gears spec'd yet. I bought the 455 with 38k original miles, never been apart. With the help of this (and other) forums, I am trying to spec out the new engine build, factor in the trans, and then decide on gears for the rear. I currently have an open 10 bolt in the 442 now. I do have a 72 Chevy 12 bolt out of my Chevelle sitting with a 3.31 posi but I may just sell that one and put the money into the 10 bolt. I am going for a very original looking vehicle.

The goal of this build is to do Rt 66 in a year and a half with my wife. She has been bugging me for years that she wants to do this run so of course I need to build the car for the trip! We know what happens if the car breaks down with the wife in it. Oh yeah, the A/C needs to work too even though it's a vert.

Thanks guys for the help.

jensenracing77

here is another option. i have no idea anything about it. but thought i would let you know

http://www.riversidegear.com/categor...oduct-166.html

Jamesbo

I assume you know route 66 is not complete anymore. In places in Arizona, I had to get on and off the Interstate to just see parts of it.

MN71W30

Better check the crankshaft for a pilot bearing hole. Or plan on having it drilled for one.
The older I get, the more I like just cruising down the highway. My personal opinion would be a 5 speed but you will need to move the crossmember a couple inches that may affect your exhaust like it did mine. I had to mutilate the hole in the floor a little, get a 400 yoked drive shaft, and a shifter. The 4 speed will be alot easier. See where you would like your tach at 60 mph to be and go from there.

jensenracing77

i am assuming this chart is with a 1:1 last gear.

skryla

I have the pilot hole in the cank already on the one I bought.

As for th RPM's, I have 14" 70 series tires on stock rims. I'm assuming they are 26"?

Do you have one of these charts for 70mph? That would be more realistic. I guess I could just muliply by 1.167.

MN71W30

It would be unlikely it is drilled but very possible, especially if it had a 4 speed behind it. There is a hollow area for the torque converter that may fool you if your not real sure what your looking for. There are some pics floating around of the pilot bearings. Luckily 455's are torque monsters that will still perform well with longer gears. I don't think they have a 70mph chart so use your formula. The chart didn't say 1 to 1 but I think we can saftly assume it is.

skryla

Thanks, does anyone have (or know of) a detailed pic so I can compare it against my crank?

MN71W30

P1010118-1.jpg

MN71W30

DSC00506.jpg

skryla

You guys are the best - THANKS!