RPM = MPH × Final drive ratio ÷ Tire OD ÷ .002975
To get an answer, you need data on those three.
I've read references to 4,000 as the upper limit, but there are several possible reasons:
1. valve float - the intake valve will strike the piston (but should occur higher than 4K)
2. with the splash oil system reliable delivery to the rods is decreased by chaos in the pan
3. refers to iron pistons? Lots of weight flying around on that skinny rod
4. 2,500 f/m piston speed is an industry recco for sustained speed, it's 3,810 RPM for that stroke length
