Leaking rear main seal - sometimes!

quote:

Any suggestions as how to improve crankcase ventilation?

what type of rocker covers do you have?

did you mention that the PCV system is in place & working?

The valvecovers are fabricated aluminum with baffles.

The pcv system is in place and I assume it Works. How do I test if it is so?

pull the PCV valve from the valve cover & hold your finger near the suction hole. it should grab your finger to it with the vacuum suction

the opposite side valve cover should have a breather or tube to the air cleaner housing for fresh air intake

the PCV valve draws fresh air from the opposite side valve cover, through the crankcase pulling out any blow-by smoke with it

adding an additional breather vent to the fresh air side cover may help a little

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.