I was wondering if there is a difference in crank case pressure,when useing different oils,I was checking out my car getting ready for the new season when I noticed my intake gaskets were pushing out from the intake almost to the point of causing a vacuum leak. The car still runs strong 9.50 at 144 mph , but kind of baffeled at what could cause this. The only change I made was going to the 20/50 green oil mid season I was using valvoline racing 20/50 and never had this problem.Ive been using the shogun evac system and has always worked great , also been fighting valve cover leaks which also makes me think theres A problem. Anybody have any ideas?

How big is the motor? Also, if you are overfilled, that causes blow by. Try reving the motor against while holding the evac hose with a cigarette lighter and see if it wants to blow the flame out. If so, that's your problem.

Its a 440 with Indy 440-1 heads

If your vac pump is working and you have a valve cover leak, pushed intake gasket? yup, you got a problem. Compression check is in order, flat tappet cam? worn lobe.

If you run a sealed engine... by rights the only
air coming into the crank case is the air going past
the rings... maybe with the change in oil it doesnt
seal the rings as good as before... if the evac is
still working properly you should be able to pull
the hose off the valve cover and have a vac at revs
(use your finger/thumb to test