M20 wide box
 

My original M21 needs a rebuild so we swapped it out for an M20 box. The M20 along with the 4.56's made that little 302 wake right up. Nothing like a set of gears in a SB Chevy! The old saying goes with a sb Chevy "you can keep the hood closed cause the performance is under the trunk."

Re: M20 wide box
 

i think 456 would wake up any motor

Re: M20 wide box
 

Sammy,

Did your Z come from the factory w those gears? You must be enjoying the balmy wx that we are getting over here in Ohio.
[img]<<GRAEMLIN_URL>>/3gears.gif[/img]

Re: M20 wide box
 

I'm glad to hear that that combo is making you happy Sammy 'cause that's gonna be my setup in a few months (I hope). I have to see how the intake change works, then swap out the 780 for the 850. After that the 4.56's go in. (One thing at a time)

Kurt [img]<<GRAEMLIN_URL>>/3gears.gif[/img]

Re: M20 wide box
 

yep, one thing at a time Kurt. I would put the 56's in before the carb swap. You will want to run that gear no matter what carb you have on that chevelle. Don't go to big on the carb. 85% efficiency on a smaller carb is better than 60% efficiency on a big carb IMO. Remember the Stock eliminator boys are running 780's with vacuum secondaries on their 396's and running in the nines. MacNeish is running low 10.40's with the 780 also on his 302.

Re: M20 wide box
 

I'm smelling what you're cooking Sammy. I just know that the motor likes fuel at high rpm. The reason I say that is when we had it on the dyno the 800 DP wasn't enough for it at 6200. If it doesn't help I'll put the 780 back on. Ya don't know if ya don't try.:-)

Re: M20 wide box
 

nothing ventured......nothing gained Kurt!

Re: M20 wide box
 

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: [email protected]</div><div class="ubbcode-body">My original M21 needs a rebuild so we swapped it out for an M20 box. The M20 along with the 4.56's made that little 302 wake right up. Nothing like a set of gears in a SB Chevy! The old saying goes with a sb Chevy &quot;you can keep the hood closed cause the performance is under the trunk.&quot; </div></div>

I thought you Italians kept everything &quot;in the trunk&quot; [img]<<GRAEMLIN_URL>>/hmmm.gif[/img]

Re: M20 wide box
 

Good one Tom. I again give you some credit. Not much but some!!

Re: M20 wide box
 

I don't think M21s have any place in a street car these days. The ratio &quot;spread&quot; from 1-2, 2-3 is exactly the same on an M20 vs M21. M20 just has a wider ratio spread on the 3-4. Seems to me that M20s are a more practical choice if you are not racing and can afford the greater 3-4 rpm drop.

You can run a taller axle and still have the same &quot;feel&quot; in 1-2-3 gears. A 3.31 gear behind a M20 will have the exact same final drive ratio in 1st, 2nd, 3rd as a M21 with a 3.79 gear (3.73 if you want to talk about &quot;real&quot; ratios).