Most likely the PCV valve is your culprit. Remember, at idle, the PCV valve is sucking with the same suction as exists in your intake manifold, maybe 14-18 in/Hg. That is definitely enough to suck
oil out of the valve train. The PCV valve MUST be shielded from the
oil via a baffle. A baffle is an easy thing to make out of thin sheet aluminum. You can secure it underside the valve cover via the PCV grommet as long as it is constructed properly. Here is a simple diagram that you may find useful. I made baffles for my valve covers and they have performed flawlessly for two years now. The diagram calls for a 1 1/4" hole but you should measure your PCV valve grommet to determine the proper size. Drill the hole before bending the sluminum sheet to size. As you can see, the baffle should allow
oil to drip off the edge towards the exhaust side of the cylinder head.
