Jerry Clayton Jerry Drain back is drain back, unless you have a ball valve to block it. If the
oil tank sits higher than the dry sump
oil pump or
oil pan until both levels are the same height fluids want out to lowest. Check valve with one way will work the same way, have 2 on my fuel system. Rick L. Ps after the motor sits for a couple of minutes the vacuum should be gone in the crankcase unless you have one hell of a sealed motor.