Timing chain slack check

Hey guys,
Im picking up a new (to me) 340 car this weekend. Im going to do a basic run thru of the motor when I get it without pulling it from car. Just timing, comp test, carb tuning, etc.
I havent checked the slack of a timing chain while motor was in the car in about 25 years. Just checking to see if I remember how to do this correctly.
Line up crank with timing marks at zero, then reverse direction about 10 degrees while looking to see when rotor moves? If moves before, good. If barely moves, too much slack.
Sound about right?