Chevy 350 pcv valve pressure

From Crankshaft Coalition Wiki

I have a 84 c10 i got a 350 engine that was bored 40 with about 3000 miles on it and ran fine. I put a set of chevy bow tie heads on it with a mild lift cam and matching valve springs. when i run the engine now it will run fine then just stall out. when it stalls i can hear air excaping from the pcv valve and when i pull the valve out it has tone of presure behind it. when i try to restart the engine it will crank really slow if i dont releave the prussure that was built up. when i pull the pcv valve out of the valve cover and then start it cranks fine. the engine will also back fire when the pressure is built up. i checked the valve and the ball moves fine and tryed replacing it with a new one. has any one had this problem before?