First, the stroke of a 390 and 427 is the same at 3.784". Why would you take away the source of crankcase ventilation? All engines have some form of PCV, whether it is a road draft tube, breather cap, or PCV valve routed to the carburetor base or intake for burning of crankcase gasses. You need to plumb some kind of positive crankcase ventilation system, or at least re-install a breather, either on the manifold, or in valve covers. The blow-by of your rings will continue to blow out the gaskets, and create leaks everywhere. Joe-JDC.
