Forum » General Engine Building Discussion » Crank case pressure

Crank case pressure

General Engine Building Discussion

Talk about engine building here. New products, tricky questions or showcase your work - If it's engine building related it's welcome here.

Page 1

my question is how do you determine if the car is a heavy breather with large amount of blow by or if its damaged something?

the story goes: i have a forged 3SGTE short block (eagle rods, wiesco pistons), it has about 800klms on it, running 6000rpm limit and about 13-14psi of boost from a GTX2867 turbo, normal 98 pump gas. running it in and took it to a track day at the end of the second session car spun out at turn 6 at QR (final turn before main straight). now as you can see its a factory air oil separator (oil drains back to sump) with an air filter on it, this has emitted alot of oil, enough to make it under the rear tyres causing the spin.

after it sprayed the engine bay with oil i performed a compression test and readings were 185-185-185-190 PSI and leak down was 3% 3% 4% 2% for 1234 cylinders respectively and the car has not sprayed oil since. now the head gasket has a restrictor for the oil feed to the head and 3SGTE's have 4 off 10-12mm drains on the back of the head, motor is east west and on about a 20 degree tilt.

oil pressure seems good all through the logs, not really sure what other tests (other than disassembly) i can perform to verify engine health?

what would you guys recommend?

Attached Files


any body?

I don't think the engine is damaged with those compression and leakdown results.

What I do think is that you need some better engineering on that breather solution. Perhaps you just need some baffles in the separator tank to prevent any oil coming from that line shooting directly into the air filter. I would consider sealing the tank where the current breather filter is, and installing a breather (with a small orifice to prevent any oil migration) somewhere off the valve cover. Or just change the filter to an overflow line to a separate vented catch bottle. Or perhaps fabricate a new oil separator tank with baffles and an overflow tube to a vented catch bottle.

For cars intended to road race, often a dry-sump system is required, or at least pan baffles to prevent oil from going places it would never end up in street use.

Good Luck

I'd agree with David - It's unlikely the engine is hurt. Often an effective breather system for an engine that will be used under sustained high rpm and load requires quite a lot of work. One of the things that can help is to move to a larger diameter breather as this slows down the velocity of the blow by gasses escaping and it's a little less likely to drag a lot of oil vapour with it. Like wise additional breathers can help achieve the same aim. We added a breather directly off the engine block on our 4G63 drag engines to help with this exact scenario. You do need to be a little thoughtful as to where the breather is mounted though so that it doesn't end up getting covered by the oil sloshing around under cornering or acceleration forces of the oil will just get pumped straight out.