Crankcase Pressure
 

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 !

:party-smiley-004:

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.

Thats what I was getting at too!

Could have that high of compression if your lifters are leaked down. Did you run the engine before doing your compression check?

The motors are 8.5-1 CR. I spray a little WD40 in the cylinder prior to doing the compression test. So, that will increase the number a bit. Experience tells me that dry compression is 175psi (no WD40). I did not run the motors before the compression test.

The break in ive always do is....run motor to operating temp (usually 10 min.) Let it cool to ambient. Run motor 15 mins at 2000 to 2500 rpm, let cool again. then run motor 20 mins at varying rpm with some quick increases and decreases but never idle. Let cool and your ready to run or dyno. there are alot of theories on break in. I have always had good results from this one.

ttt

I did a leak down and the most I saw was 10% at 100psi. Most cylinders were at 8 or so. I pulled the vavle covers and added a large breather to each one. I cleaned the motor compartment and went out for another run. Seems to have very little blow-by at all now. BUT, one motor now has a low oil pressure issue. Starting up it is fine 50psi or so then when it warms up it slowly decreases to about 20psi when above idle and at idle it is darn close to zero. So, as soon as I saw the pressure below 20 I shut it off. Does this sound like a oil pump failure? I tested the oil pressure sender it checks fine. I pulled the oil filter and it looks normal and i spun the motor over with an open oil line and it does pump volume. I'm now wondering if the bypass in the pump has been damaged.

Did you chisel the oil filter open to look for bearing material between the pleats?

No but I plan to. I am pulling the motor and gonna go with new anyways. It is cheap insurance and I know it ran for a bit with very little oil pressure. I just dont understand what the problem is and want to figure it out before I rebuild. If I dont I am certain to have this issue again.

I just finished a job last night replacing the oil pressure sender on my sb engine. It was reading low OP. 20psi at wot. Cut open the filter and all was good. Put on mech gage and had 75psi at wot. So it is possible you have nothing wrong. Also, it is common to get some blowby on force induction engines. Mine with superchargers are pretty good but a lot of guys have to run large oil catching breathers to manage the blowby/oil spray. Do a search on breathers and you will see a lot of talk in that regard.

I tried a different pressure sender and it gave me the same read pattern. I also have 2 other pressure switches (one for a dash light and the other an alarm). When I was test test running they never indicated an issue, but in the driveway at idle they do. So, I don't think it is an easy fix.

The oil filter will tell the story. But it sound like you are correct unless there is some sort of electrical problem.

You need to throw a mechanical gauge on it - the electrical gauge might have an issue. But it is suspect that it is suddenly reading low.

Oil filter full of bearing material. Pulling to down tomorrow.

Major bummer but at least now you know. A word to the wise, replace all rubber oil lines and oil cooler. Look closely at the piston skirt also for bearing material. It gets in the skirts and wrecks them.