[s-cars] S6 crankcase pressure

[dgraber460 at aol.com]

On the AAN engines, should (or shouldn't)?there be a check valve somewhere to keep the valve cover and crankcase from seeing full boost?
Thinking I might have boost leak I pressure tested the system and the oil filler cap whistled like hell with only 10 PSI applied. I am getting a strong whistle during shifts and full boost, so I know I'm loosing pressure somewhere, and it seems to be the oil filler cap. Car runs fine and pulls strong, I just don't want to blow all my gaskets.
TIA


Dennis Graber
Quality Linings & Painting
Denver, CO