Originally Posted by busboy
70’ b-body, 440 with an 833 (1967), 3:55 and a 28” tall tire. The online calculators show I should be turning 2500-2600 rpm at 60mph, I’m turning 3000rpm. I’ve confirmed the cars speed with a gps so not sure what’s up with my combination. What rpm are you folks turning using a similar set up?


Verify the axle ratio if you didn't install them yourself. 275/60/15 tires?

If the axle and tire diameter check out, it's time to check your tach calibration.

Kevin