I use my leak down tester to do what your doing on assembled motors, put air into the cylinder and turn the crank so it closes the valves and tighten up scope
If the oil pan is off and no heads on the motor I use a 1/2 inch drive extension with the big end in one of the balance holes in the crank and rotate it so it hold the extension against the oil pan rail and tighten scope
more than one way to get this job done work up

Last edited by Cab_Burge; 10/09/19 01:17 AM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)