I found a formula to finding out what gears I should be running but need to know the RPM at crusing speed of 70 MPH. My engine is a stock 1980 Buick V6 which is rated and 115 HP @3800 RPM. The engine is for my full fendered 26 T coupe. I'll be using a 4 speed and don't want to stress out my little engine. Will be using a S10 rearend 3:42 or 3:73 and 28" high tires.

Formula: RPM X Tire height =
__________________________

Gear size X 336 = and divide into the above number equals speed

Sooooooooo

I'll take a guess at 3000 RPM X 28" high tire equals 84,000

Gear size 3.73 X 336 = 1,253.28 divided into 84,000 = 67.02 MPH
or
Gear size 3.42 X 336 = 1,149.12 divided into 84,000 = 73.09 MPH

Soooooooooo does anyone know the RPM of a 115 HP engine when crusing?
How about low HP Flat Heads?

Tall Tom ........... but now because of my stupid computer - Tom F

PS Sure would like HemiTcoupe to get a hold of me!!! I have lots of questions for him.