FWIW, after installing an Edelbrock Performer RPM intake, using just the valley pan, I had oil getting down in the cylinders. The intake fit just fine. Oil was getting sucked from the valley to the cylinders. I was told the oil problem was caused because of aluminum and iron expanding and contracting at different rates. Took it off, replaced the valley pan and added a paper gasket to each side. No more oil problem. Just saying.