When distributor timing is far advanced, say 30 degrees, the motor cranks hard. On cam timing, go to top dead on #1. Just past top dead, the intake valve should start to open, meaning the valve should be about .050 open, which you can eyeball, close enough for a stock motor, but you should use a dial caliper, especially for a modified motor. From there that should tell you whether to advance or retard the timing on the cam.