please tell me at waht pressure will this open, I am going to add this to my oil fill cap
Do you have any pictures where others drill a hole to gain access? Most of my issue is at idle and I have yet to try cleaning that orifice.Yes. . I suppose you could install a PCV ball valve on the top of a drilled out oil cap. However, even that could become fouled with the typical yellow oil/water emmulsion that build up under the oil cap in cold weather. Once that happens it could freeze and back to square one.
From all we've seen here on the forum and other sources, the main cause of main seal blow out is the external PCV hose from the valve cover to the air intake freezing up. The small orifice (port) is more prone to getting carbon deposits and not responsible for main seal blow out. Some have drilled a hole into the intake right above the orifice and check or clean that small port with a wire periodically. They then plug the drilled hold with a screw or other means.
From what I've read, the internal orifice port is only used at idle conditions to route some vapors. It does not have the capacity that the intake hose PCV path has.