Running 7psi Procharger setup on a couple 500HP motors. Both motors fresh but mostly stock. I seem to have alot of blow by coming out the crankcase breathers. The valve covers have the baffles in them but oil is almost spraying out. I plan on making my oil fill caps breather caps. Is blow by common with this set up or do I need to pull the motors apart and inspect the rings? I did the break-in procedure I have always done with new rebuilds. The motors have about 10 hours on them now.

Do a leak-down test .

i bet u have the breathers right over the rockers on both sides..switch them !

Doesnt sound like the rings seated. Do a leak down on it.

Did it have loads of blow by since new or only in the past couple hours? What are the ring gaps set at?

I would wonder if the breakin was done with non synthetic oil? I always use dino oil until breakin is done to ensure the rings seat properly.

Chesepeake Bay poker run this weekend Philm, you in?

No, heading to the beach with the boat. Running down the coast from Indian River, DE to Ocean City, MD on Saturday.

See you next weekend.

Not sure about the ring gaps... I had a well known local speed shop do the short blocks and they knew they were marine blower motors.

It is hard to say if they did it from the beginning. I did the break-in with out the chargers and used conventional oil. There was no blow by then. After I connected the chargers, is when I noticed the oil in the bilge and started looking for its source. I'd say it has gotten worse as I have run it.

I did a compression test this afternoon and every cylinder was at 200psi. I will do a leak down this weekend.

what was the breakin process? did you idle the motors much during initial startup?

200 psi? What kinda compression ratio was motor built around? Most blower motors are around 8-1 to 8.5-1 and cranking compression with a run of the mill cam is around 150 or so, just curious. I built a 502 years ago with a procharger and was never happy with the blow by, I have used zero gap rings in last few motors and they have had very little blow by/leak down, fwiw, Smitty

You could be rattling the pistons from mild detonation which can cause a lot of blow by as the rings lose control. Might want to check your tune up, and like Smitty said 200psi cranking is way high, I'd confirm with another comp gauge.