97 Z28
The car is smoking alot but only every now and then. Looked in the intake and found oil. I found the pcv valve on the driver side and shook it. It does not appear to be stuck. There is also a hose that runs from the valve cover on the passenger side to just infront of the intake. It does not appear to have any kind of check valve in it.

Any thoughts on how the oil is getting into the intake?????


Reb

 

stock motor?

 

Yes it is a stock motor. It had a short block put in but that has been more than a year ago. This started up very recently.

 

The hose running from the pass. to throttlebody is your breather tube. It is neutral flowing and because of the characteristics of the LT1 engine it is normal for oil to pass through this breather tube into the intake due to the baffle inside the valve cover not doing its job effectively. Members here have used catch cans for this problem with success. However even with the normal "oil in intake" scenario it usually does not cause a smoking exhaust that is noticeable. You may want to investigate further by taking the intake off and seeing if your cylinder head intake ports are soaked with oil (usually the cause of a bad intake gasket). As already asked, how many miles are on this engine and is it stock? It's helpful to list your mods and any other details.

 

There is a filter that plugs into the the opening in the valve cover and connects to the hose. This keeps the oil out of the intake.

Do a search for it, it aint hard to find.

 

Autozone has a Deutch BF412 that fits tight. Keeps the oil out of the intake and keeps the PCV system closed.

 

We had a short block put in about 15K miles ago. There are no mods on this engine.

Since it is only doing it every now and then, can we rule out rings?? It seems like if it were rings, it would do it all of the time not just some of the time.

Reb

 

The first thing you should do is buy/make/borrow a leak down tester and see how much leakage you get. For such a low mileage motor you shouldn't have more than roughly 15% leakage. More than 30% (depending on where the leak is) might put oil in your intake or out the exhaust.

You might want to scope this quick little summary on leak down testing if you haven't ever performed this test before. I just google'd this article but it appears to be accurate.

Engine Cylinder Leakage Testing

If you do this in conjunction with a compression test and post the results back up we should be able to help you out from there.

 

You put the catch can inline with the PCV valve not the fresh air hose...

 

But when you have excessive blowby, or weak vacuum, or a missing or bent oil baffle on the valve cover, you will get oil in the "fresh air hose" and that oil will end up in the top of the throttle body, and eventually in the intake manifold. That is the oil that are trying to "catch". Its harder to see any oil that's being entrained in the PCV vacuum line, because it either dumps into the side of the manifold (93/94) or into the intake manifold under the throttle body and is not visible. There's also very little oil entrained in the PCV flow stream if the baffle on the bottom of the intake manifold is in place. Blower motors are another story.

 

Interesting, but I have to disagree. I dunno... I thought the same way after seeing oil in my intake and did a compression test. All cylinders were between 200 and 210psi along with new valve covers. There have been an overwhealming amount of posts about it here and every person I've known w/ a LT1 had always had "excessive" oil in the intake.

 

I had my catch can on the fresh air hose for the first month, and it was bone dry, litterally, not even a thin coat of oil was in it, and I beat the **** out of my car. Then I moved it to the PCV line, and it caught a few ounces of oil in 2 weeks. I did put a purolator filter on the fresh air hose just to be sure none gets through that hose.