oil in air cleaner housing

[Dick W.]

Re: oil in air cleaner housing

Thanks Dick. For my sake, I hope your's is the right answer . I will run a compression check to see if they are consistent.

A leak down test will be more accurate

[Patrick B.]

[Dick W.]

Re: oil in air cleaner housing

A good example of what this board is about. Friends helping friends

[Daniel D.]

Re: oil in air cleaner housing

Thanks Pat!

[Daniel D.]

[Edward J.]

Re: oil in air cleaner housing

Dan how about trying some stain steel coarse steel wool on the breather tube just enough to defuse the oil .it appear your tube from the air cleaner has become un attached. Maybe install enough in the tube just to see if this works.i would also make sure no stray strands are loose and this not a fix just a test to see if this works. It could be the baffle under intake in engine is screwed up some how

[Daniel D.]

Re: oil in air cleaner housing

Thanks Edward. I like that suggestion. I thought I replied earlier, but am not sure that I posted it.

[Daniel D.]

Re: oil in air cleaner housing

I realize this is an older thread that I started, but I wanted to provide an update on what was causing the problem of oil getting into the air cleaner housing. Hopefully this will be helpful to someone else. Pat Boyd suggested that I pull the carburetor to see if the base gasket was somehow interfering with a vacuum passage. As seen in the pictures, I had a relatively thick gasket that had separate openings to match the intake plenum. I switched to a simple paper gasket with an open plenum, and oil is no longer getting into the air cleaner housing. The port for the PCV vacuum fitting (1965 did not use a true PCV valve) gets vacuum from the hole at the center of the carburetor base. You can see in the pictures that this hole made an embossment in the center of the thick gasket. It did not appear to me that this would interfere with the vacuum, but apparently it did.

[Joe L.]

Re: oil in air cleaner housing

I realize this is an older thread that I started, but I wanted to provide an update on what was causing the problem of oil getting into the air cleaner housing. Hopefully this will be helpful to someone else. Pat Boyd suggested that I pull the carburetor to see if the base gasket was somehow interfering with a vacuum passage. As seen in the pictures, I had a relatively thick gasket that had separate openings to match the intake plenum. I switched to a simple paper gasket with an open plenum, and oil is no longer getting into the air cleaner housing. The port for the PCV vacuum fitting (1965 did not use a true PCV valve) gets vacuum from the hole at the center of the carburetor base. You can see in the pictures that this hole made an embossment in the center of the thick gasket. It did not appear to me that this would interfere with the vacuum, but apparently it did.

Daniel-------


I do not understand how the original gasket and/or blocked vacuum could result in oil in the intake manifold. The gasket you picture appears to be the 1966-67 gasket but I don't see why it should not work for your 1965 application. In any event, an open plenum gasket was never originally used for your application and should not be necessary now.

[Daniel D.]

Re: oil in air cleaner housing

Joe,
Oil was getting into the air cleaner through the draft tube. I did a compression leak down test and established that I did not have a piston "blow-by" problem. My understanding is that the vacuum from the PCV orifice was not enough to keep oil from being drawn out of the draft tube and into the carburetor/air cleaner housing. I'm not an expert, but my understanding is that the 65 PCV system was marginal since it only used a metering orifice rather than a true PCV valve.

[Richard M.]

Re: oil in air cleaner housing

Oddly this reminds me of fuel that collected in the intake after heat soak diagnosing carb problems. Oddly, it formed a oily residue when it cooled.

Example: '67 427 (new)Holley tripower issues when breaking in the cam first run. Turns out there was foam packing material blocking internals in the primary carb causing rough running. At first I thought it was oil. Smelling the residue was fuel. This all happened without air cleaner installed, however PCV was installed.

After I solved the carb problems all was cleaner.

Rich

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[Frank D.]

Re: oil in air cleaner housing

Sounds like the rings have not seated. Going back to the old Doctor of Motors (Perfect Circle Piston Ring book), get the engine warmed up, take it out on the highway, accelerate from 30 to 60 mph, repeat multiple times. Old chrome rings were very hard to get seated. Years ago on HD engines we actually would feed a mixture of Bon Ami and diesel fuel in the intake to get the rings seated.

Boy that brings back some memories.

[Patrick B.]

Re: oil in air cleaner housing

Joe --- Our thought process was that clean air from the air cleaner is supposed to be drawn into the crankcase at the rear of the engine by the removal of oily air from the oil filler tube through the manifold vacuum fitting on the side of the carb. If instead, oily air was going into the air cleaner and depositing oil, the intended air flow was not strong enough in the direction away from the air cleaner. Since the correct flow of air is driven by the manifold vacuum at the carb fitting there must have been too much restriction of the air flow into the carb fitting. The fitting has a built in restriction orifice.

We got a sacrificial repro carb fitting and drilled a larger hole in the restriction orifice to test the theory. The oil deposits into the air cleaner were reduced but not eliminated. It suggested that there was still too much restriction in the air flow through the vacuum passage. Running out of ideas, we looked at the gasket and apparently the amount of the crushed gasket protruding into the vacuum passages in the carb baseplate adds to the restriction of the crankcase air flow that was backing oily air into the air cleaner. A thinner gasket reduces the intrusion of the gasket into the baseplate passages and increases crankcase air flow.

As you have said, the 65 327 PCV system is marginal, and it doesn't take much to throw it out of balance. Oil in the air cleaner means that there is not enough air flow away from the air cleaner and into the carb vacuum fitting, and subtle restrictions matter. I'll bet other 327's with oily air cleaners would benefit from a thinner baseplate gasket.

[Daniel D.]

Re: oil in air cleaner housing

Pat, thanks for your further explanation. Richard, your pictures and explanations are always appreciated. That must have been interesting to find that crud in the the carb bowl and jets.

[Joe L.]

Re: oil in air cleaner housing

Joe --- Our thought process was that clean air from the air cleaner is supposed to be drawn into the crankcase at the rear of the engine by the removal of oily air from the oil filler tube through the manifold vacuum fitting on the side of the carb. If instead, oily air was going into the air cleaner and depositing oil, the intended air flow was not strong enough in the direction away from the air cleaner. Since the correct flow of air is driven by the manifold vacuum at the carb fitting there must have been too much restriction of the air flow into the carb fitting. The fitting has a built in restriction orifice.

We got a sacrificial repro carb fitting and drilled a larger hole in the restriction orifice to test the theory. The oil deposits into the air cleaner were reduced but not eliminated. It suggested that there was still too much restriction in the air flow through the vacuum passage. Running out of ideas, we looked at the gasket and apparently the amount of the crushed gasket protruding into the vacuum passages in the carb baseplate adds to the restriction of the crankcase air flow that was backing oily air into the air cleaner. A thinner gasket reduces the intrusion of the gasket into the baseplate passages and increases crankcase air flow.

As you have said, the 65 327 PCV system is marginal, and it doesn't take much to throw it out of balance. Oil in the air cleaner means that there is not enough air flow away from the air cleaner and into the carb vacuum fitting, and subtle restrictions matter. I'll bet other 327's with oily air cleaners would benefit from a thinner baseplate gasket.

Patrick-------


I can say this: the exact same oil in the intake manifold condition seen in the above photos and oil in the air cleaner can be found in many engines using PCV valves such as the 736C and 746C. So, I do not think it's uniquely related to the unusual and marginal PCV system used for 1965. My 1969 350-300 evidenced it from day-one.