no you should not hear compression leaking during slow cranking. you shoul dbe able to hear compression leaking during a turn of the crank with a breaker bar, PSSSssssss.....but not during a crank session unless your starter is really laboring and your start RPM is like <100...even that is > 1 rev a second..not enough to bleed out I would say. Man, pull those valve covers and check the lash and then valves heights across with no rocker shaft.