Oil in the air cleaner...HELP!!

[Dick Kindl]

All you expert motorheads!! I have a 66 with a 327/350HP. When running at high speeds, (over 60MPH / let's say around 3000RPM), I get a lot of oil in the air cleaner. The oil spills over on the intake after filling up to the lower rim, and the air filter gets saturated with it. My oil pressure is pinning on the gage ..it drops back a little at idle. I took the air-breather tube off( as recommended by a friend) and looked in the hole w/a mirror and was told I should not be able to see the push-rod- and if so, was missing the internal oil breather canister that is supposed to be in that hole. I did see the pushrod so I assume that the canister is missing and this is why the oil is being "sucked" up into the air cleaner. I have obtained such a canister and will be installing it.

My question? Is this the cause of my problem or should I be looking at other solutions as well? I checked the PCV valve and it is OK. Any help will be greatly appreciated.. Thanks in advance....DICK

[Clem Z.]

Re: Oil in the air cleaner...HELP!!

buy a genuine GM PCV valve as some aftermarket ones cause all kinds of problem including oil burning

[Mike McKown]

Re: Oil in the air cleaner...HELP!!

I won't say the missing baffle is causing your problem but it is likely aiding and abbetting it. If memorey is correct, the PCV valve is in the oil fill tube at the front of the engine and is plumbed to a vacuum source on the carb or intake. The flow should run out of the fill tube into the vacuum source with fresh air vented through the rear of the crankcase which is piped to the air cleaner. If you have oil in the air cleaner, your flow is reversing for some reason.

[Joe L.]

Re: Oil in the air cleaner...HELP!!

Dick-----

In the PCV system used for your engine, filtered air is drawn from the air cleaner through the tube in the rear of the block, into the crankcase, and then out through the line in the filler tube to the vacuum fitting at the base of the carburetor. However, the lifter valley mounted "cannister" is really an oil baffle designed to prevent the "reversion" of the oil mist ever-present in the lifter valley of a running engine from "back-flowing" into the air cleaner. If this baffle is missing from your engine, then that's a really good potential culprit for exactly the problem you're dealing with. I' definitely install it at once.

Your high oil pressure problem is likley unrelated to this problem, but it may constitute another problem in itself and for other reasons. The first thing that I'd do is to hook up an accurate test gauge to determine if you really have a high oil pressure problem. If you do, we'll go from there.

[Duke W.]

Re: Oil in the air cleaner...HELP!!

What you refer to as a "cannister" and (I think) GM calls a "ventilator" functions as a liquid vapor separator, and if it is missing I would expect oil in the air cleaner.

Removing the manifold to place the device there should solve the problem, and you should also research the appropriate service manuals and AIM to insure that your PCV system is properly configured with proper routing and parts.

Duke

[Joe L.]

Addendum

Dick-----

One other thing: even with the cannister/oil baffle installed, don't expect the "oil-in-the-air filter" problem to go away completely. Under certain engine operating conditions, some of the oil will get back through the system and into the air cleaner. These baffles just aren't that efficient.

In 1968 the system for small blocks was revised so that the rear of block breather was eliminated and "intake" for the PCV system was moved to the right side valve cover and the "suction" moved to the left side valve cover. Baffles in both valve covers were supposed to prevent the excessive escape of oil. They weren't too effective, either, and GM changed the design of the baffles 2 times to help improve the situation. The problem was never solved, though, and some oil will usually be seen in the A/C. My 69 has been doing it since the day it was new and even though I "upgraded" the valve covers twice to take advantage of the "new and improved" oil baffles.