It should stay open. Unless you put in a pvc system. The draft tube that is supposed to be there has a goose neck and extends straight down to the bottom of the car, with a bologna cut on the end that draws out the vapors as the car goes down the road (venturi effect) Don't close it off, it's needs to stay open so the vapors in the crankcase can get out. Unless you put in pvc system, then the vapors are sucked into the intake and burned and sent out the tailpipe.