When I used to race my 13 second dart 340 many years ago, it would not leak oil per se but after a 1/4 mile run, the valve cover would be moist, occasionally the dipstick was pushed out an inch, the main seal was wet.
I put an evacupan system onto the header collector and all this seepage went away. My new 10 second w2 motor will have a belt driven vacuum pump for even more vacuum for hopefully a small power increase as well. Crankcase pressure can cause these issues.
