Well, here I am back again. Just confirmed the gear ratio on the Camaro diff going into the 39 Chevy is 342:1. I believe the diff gear ratio on the 60 Pontiac from which I harvested the 261 engine and 3 speed standard tranny was 355:1. The car from which parts were harvested was a 60 Pontiac Strato Chief, 4 door sedan. In order to obtain optimum highway performance I would like to know:
a) What was the tire diameter on the bias ply tires that were originally mounted on the Pontiac?
b) What is the engine RPM the 261 is most comfortable at when operated at sustained highway speeds?
The information will help me to determine the best tire size to mount on the 15" rims I intend to use on the Chevy.
.....on my 49 truck that I just did, I used 215/70x14 in front and 235/60x15 in back, they are same height. You need to see how much room you have for rubber before you pick a size. 60's are wider than 70's wider than 75 series.
-- Edited by Johnny Ringo on Saturday 28th of June 2014 10:10:35 PM
.....on my 49 truck that I just did, I used 215/70x14 in front and 235/60x15 in back, they are same height. You need to see how much room you have for rubber before you pick a size. 60's are wider than 70's wider than 75 series.
Don't forget.. that if you are trying to be "perfect" in your sizing (some are)
that 775-14 bias ply or any bias ply may the same height as the radial you pick out
BUT radials have a different loaded static height
example a 28 inch "bias ply" may sit 14 inches from the middle of the rim to the ground
and a 28 inch "Radial ply" may sit 12.5 inches from the centre to the ground
Thats the distance that affects your gear ratio.......
