trumps2000

iTrader: (2)

Twice this month, I've found my car down two quarts of oil. Its not leaking so I checked the plugs, all gummed up. Now this motor is a new GM crate with ~1000mi, so I doubt its blowby or valve seals. I think the oil is coming through the PCV. Has anyoneelse come across this problem? Whats the solution?

The PCV valve is new and has the rubber hose run straight to the qjet. I also have an Edelbrock breather on the other valve cover.

Mkos1980

iTrader: (8)

Naw.. My vote is intake gaskets.

Air_Adam

What valve covers are you using? Whats the baffling inside like? Some aftermarket valve covers have really poor baffle designs, if they even have baffles at all. GM valve covers have the best baffle setup.

trumps2000

iTrader: (2)

I'm using the valve covers GM supplies with the crate motor. Its got baffling, not sure how good. After posting I took the PCV hose out and looked at it under the light. There is a residue of oil on the bottom of the hose. My friend suggested I use a glass filter to catch any oil so that I can be sure its the culprit.

To fix it I've heard of people using catch cans, does that really work? I was thinking of epoxing one end of the PCV hose fitting then drilling a smaller hole to reduce flow. Think that would work?

TexasSilhouette

iTrader: (4)

Barking up the wrong tree.

Blocking the PCV is not a solution, even if that were where the oil was going.

Make sure the crankcase breather is clear as PCV does not work under wide open throttle and you will need to be sure crankcase gasses have a place to go during those times. I am not familiar with the Edelbrock breather but I suspect it is one of those designed to spew crankcase gasses out all over your valve cover whenever you mash it. Make sure air flows thru it both ways and freely.

At idle, you should be able to feel the PCV pull on your thumb covering the VENT hose after a few seconds.

With that checked, I would think your PCV system is operating reasonably well.

Remember, new does not mean good

Gumby

Do you have smog checks and stuff?

If not I would ditch the PVC and just install single or dual filter in the valve covers. Let then engine breath free so it can't build pressure and puke oil.

But if you got smog you better get it fixed right and ya may end up needing to deal with GM if something was done wrong.

Nothing wrong with a GM crate but I would avoid assembly line crates like that if you can.

Air_Adam

Thats not going to solve anything... PCV helps keep crankcase pressure way down, which is good, and helps ring seal, which is also good.

If you do ditch the PCV, don't be surprised if it starts to consume more oil because of less ring seal, and the oil gets really dirty in an unusually short period of time.

Brian Murray

Replaced an intake recently?

trumps2000

iTrader: (2)

Well I did install the intake when I got the motor. But I have lost 2qts in ~250mi, I don't think the intake could suck up that much oil. Also I've found an oil residue in the bottom of the PCV hose and in the PCV valve, making me 99% sure thats where its coming from. I'm using the GM valve cover and it does have the baffle.

I ran across a gm pdf document that mentioned one reason for excessive oil loss is continuous WOT driving. any ideas why? Since I got this car back together I 've had my foot into the pedal. (Haven't driven a V8 in a long time)

Gumby

You typed that backwards, PVC helps keep pressure up to help "ring seal" not down. If down was the key...... filter that vent free [like ya see on every hot rod] keep the pressure down to nill as the engine breathes/vents free.


If your really worried about ring seal you run the engine like a sand drag.
You run a piece of steel hose from near the end of the headers to each valve cover. The exhaust pulses then help keep pressures equal above and below the piston. There is also some fancy trick using a vacuum pump on the crank case to do the reverse. I member some threads here about folks trying to use smog air pumps in reverse ot avoid spending $300 on the right vacuum pump.

trumps2000

iTrader: (2)

The carb pulls a vaccum and sucks air through the engine, so I would think it would reduce the air pressure underneath. Though the breathers seem pretty free flowing.

As far as ring seal goes I guess its better because on the intake stroker the cylinder is pulling a vacuum and the difference in pressure makes it harder on the piston to move down in the bore?

Gumby

Only reason they hook it to the carb is for EPA reason to reburn them nasty oily gasses.


My V6 3rd gen has the complete PVC system but it does not vent that crap into my intake. I plugged the hole and run a mini filter on the end of the hose.

Brian Murray

My vote's the intake gaskets, since you say you swapped intakes.

When I swapped intakes I was losing oil really quickly too, about a quart every two hours, so I'd go through about 4 quarts of oil every 300 miles. Turns out that the intake vacuum was sucking oil up out of the crankcase through the lifter valley and burning it.

Check your exhaust for an oily smell at idle, and check your tailpipes for an oily sludge by running your finger along the inside of your (cold) tailpipes.

I replaced my manifold gaskets with copious quantities of RTV and now I have no leaks and my oil stays where it should.

Gumby

Even the pro's use lots of goop on the intake.

hi tmep copper RTV is good for anything. Have used it on water pump and was driving in 20 mins.

Air_Adam

Precisely... the PCV system creates a negative pressure inside the engine, and thats when helps ring seal. It also helps to keep the oil clean because it 'sucks' out contaminants in the fumes inside the engine, which include unburned fuel (blow-by) and condensation.

The best thing a pair of breathers will do is attempt to keep the inside of the engine at atmospheric pressure, but very rarely can.

trumps2000

iTrader: (2)

I think Brian might be right about the intake gaskets, at least I hope so. I put the glass filter inline with the PCV and only noticed a few drops of oil not tons of oil. I checked the oil after about a 40 imile trip and I believe its sucked in more oil.

I'm going to check the compression just to make the rings and valve seals aren't blown. Brian did you notice any other driveability problems? I've been having a bad stumble when I really stomp on it and no matter how many times I check/ fix the carb, it never goes away. I wonder if this is a sign of that.

trumps2000

iTrader: (2)

Just to update I did a compression test on cylinders 2,3,4,7 and got readings of 145-150, so I believe the rings and seals are fine. I'll swap the gaskets in the next month and while I'm in there I'll pop in a new XE262 cam.

Air_Adam

145-150 is just fine. Not stellar, but not unhealthy or unusual.

TexasSilhouette

iTrader: (4)

PVC=Polyvinyl chloride, a plastic commonly use in among other things, plumbing plastic.

PCV= Positive Crankcase Ventilation, A method of assuring combustion gasses (including water) are evacuated from the crankcase.

PCV Reduces crankcase moisture and fuel, extends oil life and reduces crankcase sludge. It will also remove accumulated fuel that is particularly important on a carbureted motor where gasoline contamination of the oil is normal.

PCV allows the higher atmospheric pressure to scavenge the crankcase on its way to the lower pressure of the intake manifold. It does this by LOWERING the pressure in the crank case. The fact that those gasses that would otherwise stink to high heaven are consumed by the engines combustion is a bonus as it prevents our having to breathe or smell them.


Header breathers use the pulse air effect to LOWER the pressure in the crankcase. This is a form of PCV in that you are using the lower pressure at the header flange to drop the pressure in the crankcase so that atmospheric pressure scavenges the combustion gasses from the crankcase. This method is effective on engines that have very high intake pressure (low vacuum) and can continue to purge the crankcase in some cases even under wide open throttle.

trumps2000

iTrader: (2)

Well its been ahile, but I hate to leave threads untied, as I learn from other people solutions too.

Mkos1980 and Brian Murray were right. While upgrading my valvetrain I took the intake off and found softened paint on the mating surfaces of the intake! I bought this performer off of Ebay, and I could tell it had been painted, but didn't know it was painted inside and out! Well I scraped the surfaces clean and used RTV to seal the ports. Since I've got her going again the plugs are reading good, got that nice tan color and NOOO oil.

Thanks, all for the help