The 305 in my roadster pickup is blowing oil out of the dipstick tube at sustained speeds of 50 to 60 miles per hour---enough to really mess up the passenger side of the car. This is a chrome aftermarket dipstick tube, and chrome aftermarket dipstick. I know that the engine was not doing this when I pulled it from the donor car 16 months ago. I was trying to do some diagnostic work today, so I took my vacuum/pressure gauge, and hooked it to the dipstick tube. There is zero vacuum or pressure at the dipstick tube thru the full RPM range. I have a vented oil filler cap in the passenger side valve cover and a pvc valve in the drivers side valve cover, with a vacuum line running to the bottom front vacuum port on my 4-barrel quadrajet. I tested the vacuum on the port from the carb, and it is pulling 22 inches of vacuum at idle. I pulled the pvc valve (its a new one) out of the valve cover, and "sucked" on the end which attaches to the vacuum line, and it passed air with no restriction. This seems to tell me that there should be enough negative pressure inside a good running small block crankcase to avoid any kind of pressure build-up which would force oil out the dipstick tube. The only strange thing that I noted was that when the engine was idling and I pulled the hose off the PCV valve the engine immediately stalled.---Now---if I could suck air freely thru the pcv valve, then the carb should be able to suck air freely thru the pcv valve also. If the carb can suck air freely thru the pcv valve, then the engine should run the same whether the vacuum line is hooked to the pcv valve or pulled off of it. I don't really understand whats happening here.---any wise suggestions? I took out the dipstick and plugged the dipstick tube, then drove around to see if that really was where the oil was coming from-----there was no more oil showing up on the side of the car after that, and no oil leaking anywhere else.