I am apparently drawing more air into the crankcase than the PCV valve can expel, so I am getting oil out the dipstick at high RPMs. This is after replacing the oil cap because it kept popping off; now that it stays on, the pressure is being relieved a different way.

I've had one or two suggestions from people, including my mechanic, but most of them aren't really that workable or need something potentially difficult to find. I'm wondering if anyone else has faced this problem and what they've done about it.

I've been told to:

- do away with the PCV system, cap the port on the TB, and run open breathers. This, however, has the potential to spray oil all over the engine compartment if it does get overpressured.

- dump the PCV system to the headers instead of back to the plenum. However, since my car has a MAF I'm now removing metered air from the system. Plus, it'll kill any chance I have of passing emissions with all that oil. Plus, I just had the headers coated and am loathe to put a bung or two on them...

- replace the new oil cap with one that has provision for a PCV valve (I'm told they exist, but may not be easy to find), and connect that valve to a dis-used port on the back of my SuperRam plenum (where the MAP would connect if I were running one). Problem here is finding the oil cap.

- get a second passenger-side valve cover and put the second PCV valve there. Downside is that we finally stopped the leaks from under the cover so I'm trying to avoid removing one. I will if I have to, but I'd prefer an alternate solution - aside from the fact that it may be difficult to get just one ProForm cover without getting another set.

- I've thought about removing the PCV valve altogether and running a breather with a large-diameter tube to the above-mentioned port on the back of the SuperRam. Not sure what effect this will have on the computer, since I'm told it actually knows about how much air is let back in by the PCV valve.

Part of the problem, I think, is that the SuperRam uses a smaller-diameter hose and nipple feeding into the manifold than the stock one, because of fitment. That narrower hose may just be too small for the extra air that needs to flow, where a stock one might have been ok.

Has anyone else done anything different?

Many thanks.
[RICHR]

 

I'm sure this sounds smartass but LT1/4 engines don't seem to have a problem with PCV. Just a valve and a tube. I see a bit of oil residue in my semi-clear tube but nothing more.

No problems here with rpm up to 6800 and well over 10K miles.

Sounds like you have a basic PCV valve problem. Oil out the dipstick tube is definitely not right.

Engine specs may help.

 

Rich,
Are you using the original PVC valve or did you get a replacement recently? It its a replacement, it may not be correct and have the right size orifice.

Is your intake manifold leaking oil too? That may not be from overpressure, but just from missing caulk. I hoped to reduce the amount of oil leaking on mine by using a vented oil cap. It had no consequence, it still leaks oil, so its not an overpressure.

Leaking out the oil level tube sound like overpressure, or oil level too high. On marine motors the tube extends to the bottom of the pan so that you can suck the oil out for an oil change. On auto engines the tube usually stops just below the block. So if liquid oil is coming out, the oil level may be too high, and you are getting foaming further increasing the oil volume. That will push oil out, as well as overpressure in the crankcase.

My bet would be that the PVC valve is not the correct one, since I have not seen you mention this before in the few years of seeing your posts.

Rich

 

Another thought: do you have any water in the crankcase? That would increase the volume of liquid and cause oil to blow out, too.

 

Excessive crank case pressure, popping out the oil tube, and such is usually caused by excessive blow by of the rings on high mileage engines with worn rings.

Some higher compressions or forced induction engines will have exceesive crank case pressure too by thier nature at high RPM's.

The PCV valve is not open unless under vacuum and is not designed to relieve excessive crank case pressire. There are crank case breather tuebs for this, but the size of the outlet can be restrictive.

On some of the turbo charged cars that I have ran I have had to open up the breather tube to a much larger size hole and then end up running it to a 1qt size catch can setup insted of back into the intake. Don't let DEQ or emmissions testing see this or you won't pass so it best be well hidden! Summit makes a qt size container for this. Just look up catch cans. Solves the problem of an open breather with spraying oil mist all of ther place...

 

More info...

The engine is a rebuilt 91 roller block with higher-compression heads (higher than my original 86) and a SuperRam plenum/base. I don't recall what the compression ratio actually is, but it's not stock... The PCV valve is the original one, but with a thinner hose leading back to the manifold due to the design of the SuperRam (it's not a LOT thinner, but it is not the same ID). The rings are fine (compression test) and are new (moly plasma, FWIW).

There should be nothing in the crankcase but oil; no leaking gaskets (again, everything is newly rebuilt) and the oil's been changed a couple times as the engine breaks in. Nothing unusual there.

Too much oil? I think I've got 4.5q in there, which should be right for this block and filter.

Basically, the problem has developed since the installation of the new engine (which has roughly 1200 miles on it now) so that's why I've never mentioned it before .

Fortunately, our emissions people don't check under the hood (though they do use the evil treadmill) so I can mod there to my heart's content.

Thanks.
[RICHR]

 

The only air that is DRAWN into the crankcase is due to the lower pressure created by the air removed by the PCV valve. Any other air entering, isn't being DRAWN. The oil caps poppong off and oil coming out of the breathers and dipstick are evidence of pressure, not the vacuum that could DRAW air in. Your crankcase is pressurized and there is only one possible source of the pressure. Blow by. Compression test aside, there is something wrong with your rings. Broken, cracked, upside down, not yet seated, rings? Something is allowing compression and/or combustion pressures past the piston rings to pressurize your crankcase. There is simply no two ways about it. You might try a cylinder leakage test if you are still skeptical.

RACE ON!!!

 

Unfortunately that is absolutely correct. I had blowby also and it was the rings that were to blame. Just do your basic diagnostic tests as it's not a breather problem.

 

Huh. I had a leakdown test performed a couple hundred miles ago, and everything was fine then, according to the mechanic. I had the leakdown done because I had one fuel injector that got installed wrong and it was leaking gas into the cylinder when it wasn't supposed to, so I was worried about the cyl. wall getting washed down.

I do have a high-volume oil pump installed; he thought that might be contributing.

I guess I'll have the test done again. I'd have thought, though, that a ring problem would show up at lower RPMs as well. Is it just possible that the rings haven't seated yet at ~1200 miles? Someone did say that moly plasma rings take longer to seat. It'd be great if this were a problem that resolves itself with more runtime. "Honey, I need to finish breaking the engine in. See ya tomorrow! "

Thanks.
[RICHR]