The better PCV do need a minimum, how much I don't, vacuum to keep them open. The cheaper ones will stay open most of the time when the motor is running shruggy
All of them I've seen and cleaned have a check ball and spring to close the ball when the motor is not running, not all of them will seal up when not held open by vacuum shruggy

Last edited by Cab_Burge; 10/20/17 05:02 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)