81 Chevy 305H motor oil leakage prob

[mattopia]

I have a 305H in my 81 Chevy SWB and Ihave a problem with the oil foaming up out of the valve covers into the pcv valves. All the vacuum lines are hooked up right. It has Edelbrock valve covers on it. The motor is stock otherwise. It runs great it just leaks oil from these spots. The heads are not cracked. I am not loosing coolent. When I drain the oil it comes out normal, no foam. If I put a push on oil breather on it pushes oil out of it too. It also comes out the dipstick tube. Do these High Performance motors need the tall valve covers? Is there a blockage? Thanks for any help.