Jay, what kind of motor bro? A big block Chevy approx 3/8", a small block Chevy like 1/4", dont know about the Ford stuff, but betting this is close...
A good way to test this is with a degree wheel on the crank and rotate the crank with a breaker bar, you should not see more than 2-3* of crank rotation before the rotor moves...May need to move it back and forth to get a good read.
GT