I've had this problem for awhile ever since I put a more agressive cam(actually kind of mild 218/224 duration. >050). At speeds of 90 or higher my engine blows of pushes out oil from the oil filler tube or vent on my valve cleaner. I'm running a hose from my oil vent in my valve cover to my carb to take care of some blow by, but can't figure out how to fix this proble. My 305 is running a dual plane intake with a 600 cfm edelbrock carb. It's been bored .060 over with 10.1 pistons. The cam makes it idle pretty lumpy and I have a stock converter in place with my 350 tranny. My total timing is 36 degrees. Even with the high gears of 2:76, my 37 runs hard and it's pretty quick in the quarter at 103 with these gears, but after a run my engines is covered with oil.