Long post, sorry. After doing a lot searching here and other forums, I thought I would throw out my question concerning backpressure and crankcase pressure. Is it possible to have excess crankcase pressure at higher rpm's due to a constrictive exhuast y-pipe? The reason I ask is because I have had the same problem with 2 different motors in the same car and the common denominator is the y-pipe that comes off the shorty headers. The first motor was a built 355 that would blow oil vapor all over the passenger side valve cover, with or without the pcv in place of 2 breathers as well as a small leak from the back of the oil pan and it was not the main seal. I sold that motor to a friend who dropped it into his car and he had neither problem with the motor. I built the 406 that I dropped into it this spring and the exact same problem with oil vapor and small leak at the back of the oil pan with or without a pcv on this engine. Right now I am in the process of putting a breather catch can assembly in to at least capture the oil the accumulates from the breather. There is no motor problem, I am not burning any oil and there is no sign of oil anywere in the combustion chamber, spark plugs, valves etc. compression is good in all cylinders with no pressure loss. I am really thinking it has to do with the y-pipe that is on the car and am saving money for long tube headers from Stainless works with their matching straight y-pipe fro 82-92 camaros. Again, sorry for the long post but I really wonder if I'm going in the right direction with this since the those headers and y-pipe are about $1100.00 and could use others input or ideas. Thoughts??