Reply to "Leaking rear main seal - sometimes!"

Momentary pulse-pressure surges affect all engines but as you say- the bigger the displacement, and the higher the operating rpms, the more pressure surges tend to affect engines. Old Triumph bikes and H-Ds both with overbore kits come to mind. 500-inch Pro-stockers run at 9000 rmps are severely affected, and I've known of some supercharged 351-Cs that regularly fogged up the rear window in a Pantera with oil from the front main seal when under even mild boost. Likely, the fogging was also oiling the clutch from the rear main but that's not visible. Off-boost, no leak at all.

Unfortunately, such pressure surge problems have no one-size-fits-all solution. What works for one motor may have no effect on another- or some negative may appear. It seems to be allied with how tightly the crankcase wraps the crank & rods, how much oil is flying around inside- which itself is affected by con-rod side clearance, oil pressure and probably many other things. Blow-by is simply poor ring seal and thats a serious problem all by itself. Good luck and let us know if you do solve the problem.