[unruhjonny]

Wow!
I keep getting more and better information!
Sweet.

I had never thought that the 2-3 shift in an M-20 might hurt the E/T - then again I have (gasp) never driven an M-20 car, only M-21 & M-22.
I have had some time to chew on it, and the more I think about it, the more I like the idea of re-degreeing the camshaft... That had never occured to me, and for some reason I figured that was a no-no...

1.65 rockers huh...
I had figured that was a definite no-no, as it works out to something like 10% extra lift...
I might have a set of stamped steel 1.65 rockers...

[Formulajones]

Originally Posted by unruhjonny

Wow!
I keep getting more and better information!
Sweet.

I had never thought that the 2-3 shift in an M-20 might hurt the E/T - then again I have (gasp) never driven an M-20 car, only M-21 & M-22.
I have had some time to chew on it, and the more I think about it, the more I like the idea of re-degreeing the camshaft... That had never occured to me, and for some reason I figured that was a no-no...

1.65 rockers huh...

You mean the 3-4 shift......Dennis mentions this being a factor for the RAIV cars. They are a little more high strung, like more rear gear etc...and will need that rear gear to get the car going with an M-21 (2.20 first gear) They like RPM and seem to make most of their time up on the back half of the track. On our 400 RAIII stuff you may find the M-20 is your friend.

May want to ask Dennis, I can't remember but there is also a spring seat pressure limit to keep guys from running a ton of pressure and gaining advantage. I can't remember what it is, might be 110 or 120 lbs. I'd have to check.

I have my 69Z setup for PS as well. High strung and likes rear gear, most likely will run better with an M-21.

[SD455DJ]

Formulajones, 130 lbs max seat pressure, unless came from factory with stronger springs and you'll need to show us the proof, but you should run the least pressure springs for the most horsepower, so it is not uncommon for the racers with the fastest cars do a lot of testing to find the minimum pressures they can get away with to maximize power. It's a fine line with some cams and a reason to run cams with slower ramps like Cliff suggests. It works at the Pure Stocks.

RAIV's, like SBC's like a lot of gear, 4.33's work great, 3.90's slow your 60' by 2 tenths along with your ET. The Z's at the race seem to gravitate to 4.88's as the favored gear. 4.56's are OK, but not enough for them there no-grunt hi-winders. The tighter you can keep 2-3 and 3-4 shift points, the better these cars seem to run.

The RAIII's are a different animal and the M-20/3.73 combo is a great starting point.

Dennis

[Formulajones]

I already have a 4.88 rearend here setup and ready to go

Thanks for the update on the spring pressure. I couldn't remember what it was and I just went through this last summer. Getting old, lol.