I have a wide ratio Muncie behind my 383 that makes 498hp at the rear wheels on a dynojet chassis dyno, and was wondering if anyone has tried a wide and a close and which one they preferred, and why. I am very happy with my M20, but will I like a M21 better? My car is just a toy, not a racecar, so I won't be doing any real hard launches. Also, is it worth the money and time to find an M22 for my application?

If you are running a lot of rear end gear it might be worth switching, however I would wait until you blow up your current trans before purchasing an M21. Do you get a print out of your power curve when you make a pull on the Dynojet? If you do it might show you how your power band is layed out. Ask the operator what they think.

Steve R.

4.10s in the rear.

I've run both back to back but with 3.55's and 26-28" tires. I prefer the 1st gear of the M20. But with 4.11's you might prefer the closer spacing of the M21.

your first gear now is 2.52X4.11 = 10.36
with the M21 is 2.20X4.11 = 9.042.

If 1st seems short now, then the M21 might be better.

Last year a friend of mine was runing a m-21 with a set of 3.50's(yea he had a 9 inch)behind his 355 SB.The motor was a mild combo: Lunati HYD. cam(235 .050 285 adv 507 L 108 LS)and a Weiand Stealth intake with ported 186 heads-202/160,10:1,Holley 750 DP,Hooker 1 & 5/8 inch headers.
When he would let the clutch out in trafic the car would shake and shuder.I think it was because he didn't have a deep enough rear gear and he was luging the motor.He ended up regreting his decision to run the 21 over the 20 on the street.
Now I know your 383 will make more torque to overcome the gear.Just keep your rear gear in mind if your considering this swap.



[This message has been edited by mutant 68 (edited 09-28-2000).]

This might be obvious, but a big torquey engine doesn't need much gear in the rear. It probably will slip the clutch starting though so it's life might be shortened. Bring the car out of the hole easy, get it rolling and nail it.

I used to used third and forth with my M-20 behind my 406 and stock 3.31's when my shifter needed cleaned and greased. pdq67

Bowtieusa,

Do you mind sharing some info on your engine? That much horsepower at the tires puts you at about 600 or more at the flywheel; VERY good! I'm curious is all. We're hoping one of my cars makes about that much; it only made 415 but we found out the sidepipes only have a 1 7/8" i.d. on the mufflers. They are being modified now for 3" i.d. mufflers and the car should be back on the dyno next week.

Jody

You said you wanted the skinny on my 383, so here it is: First off I run a Victor junior with dart aluminum heads, both ported and matched. Comp cams (roller) 244 duration and with the 1.6 rockers it has (can't remember exactly) around .570 lift? Primary tubes on the super comp hookers are 1 3/4, the rest of the exhaust is 2 1/2. compression is 12:1 Holley 750 dual feed. Hopefully this helps...........

Thanks, that's what I was looking for. The 406 that I will be re-dynoing should make about 580-600 horsepower at the flywheel (480-500 at the flywheel).

I also have a 406 in my 72 Camaro that is extremely close to your 383 as far as parts but unfortunately doesn't touch yours as far as power. It's 11.5-1, Dart Iron Eagle's with 215 cc ports (un-ported), Comp roller .600/ 244 @ .050, roller rockers, Victor Jr., 750 Speed Demon. I got 350 h.p. at the tires with 428 ft. lbs. It just seems low to me and has been discussed on the board here. I'm pulling it out in a couple of weeks to convert it for use with a P600B Pro-Charger I took off my other car.

Thanks again for the info.

Jody

Camcojb,

The more I get into this forum, the more I realize that its the heads that make or break the power of an engine.

It seems to me that one can run "large" unmodified heads with a big cam and leave power on the table. But if "smaller" modified heads are matched to the correct "smaller" cam, power picks up everywhere.

Seems its due to intake port velocity and air flow "quality". I wish that I knew more about this but I can't afford a flow bench much less am not inclined to figure out how to use it.

But, hey, your lung will probably put you right where you want to be anyway. pdq67

It also helps to have grown up with someone like John Lingenfelter as one of your dads longtime friends, that only lives approx 5 minutes from my home! If you know where I am coming from..............