Intake sucking oil ???? C-1

[Joe L.]

Re: Intake sucking oil ???? C-1

Edward, in a previous post, I saw where the underside of the intake was cracked and pulling oil up into the intake ports. This may be something I will take a close look at this weekend. I'm gonna try to see if the shop owner will bring his video scope over to try to look inside the intake ports and possibly the back side of the intake valves first and if not, then pull the intake. I was also told to look for loose rivets on the underside of the intake as a possible source for sucking up oil.

Al------


If there was a crack on the bottom of the intake manifold I don't think you'd see it with a "video scope". You'd probably need a magnaflux inspection to find a crack. In addition, the only "rivets" on the bottom of the manifold are those that retain the oil shield (actually, these are drive pins and not rivets but the head appears like a rivet). The holes for these pins do not go through so even if a pin was missing it would not provide a path for oil into the intake manifold.

One other thing: once-upon-a-time I faced the exact same problem you are having. I've reported on this in previous posts and I don't want to go back over the whole thing but I did everything imaginable to stop the oil intrusion problem. Among the things I did was install three different intake manifolds including 2 brand new manifolds, install a new set of GM heads, install every type of valve seal imaginable (e.g. all Teflon, Teflon/Viton, all Viton, each of the preceding with and without stock o-ring seals), every type of manifold side gaskets you could imagine, with and without several different type of sealers. As a last resort and in desperation, I re-ringed the engine (even though I had absolutely no reason to believe that the oil problem was a ring problem). I NEVER solved the problem and finally gave up. One of these days when I get around to it I'm going to "autopsy" that engine to see if I can come up with a reason for the oil problem. I doubt that I'll find anything definitive, though.

[Jim D.]

Re: Intake sucking oil ???? C-1

Al------


If there was a crack on the bottom of the intake manifold I don't think you'd see it with a "video scope". You'd probably need a magnaflux inspection to find a crack. In addition, the only "rivets" on the bottom of the manifold are those that retain the oil shield (actually, these are drive pins and not rivets but the head appears like a rivet). The holes for these pins do not go through so even if a pin was missing it would not provide a path for oil into the intake manifold.

One other thing: once-upon-a-time I faced the exact same problem you are having. I've reported on this in previous posts and I don't want to go back over the whole thing but I did everything imaginable to stop the oil intrusion problem. Among the things I did was install three different intake manifolds including 2 brand new manifolds, install a new set of GM heads, install every type of valve seal imaginable (e.g. all Teflon, Teflon/Viton, all Viton, each of the preceding with and without stock o-ring seals), every type of manifold side gaskets you could imagine, with and without several different type of sealers. As a last resort and in desperation, I re-ringed the engine (even though I had absolutely no reason to believe that the oil problem was a ring problem). I NEVER solved the problem and finally gave up. One of these days when I get around to it I'm going to "autopsy" that engine to see if I can come up with a reason for the oil problem. I doubt that I'll find anything definitive, though.

I went through the same thing. I finally solved the problem. Al, I sent you a PM. Give me a call if you want to fix your car.

[Joe L.]

Re: Intake sucking oil ???? C-1

I went through the same thing. I finally solved the problem. Al, I sent you a PM. Give me a call if you want to fix your car.

Jim------


Don't keep us in suspense. How did you solve the problem?

[Domenic T.]

Re: Intake sucking oil ???? C-1

Al,
That tells me that the leak is past the rings (hearing the leak in the case).
I use my aircraft leak down on auto engines and and it is calibrated for 80lbs for log book entries. Doing each cylinder individually takes time but tells the story, intake, exhaust, or rings. You can check the guides by moving the stem back & forth at the retainer. It would take 2 cracks to suck oil from the intake heat passage, one in the bottom and one under the carb.
If that were so the engine would have a wide range of power loss and RPM's as the manifold heated up. I would wash the oil out of the cylinders and try another compression test DRY, then squirt oil in the cylinder and check it again wet and compare dry against wet.
With bad rings you will also notice high crankcase pressure out of the breather when you gas the engine.
You can usually find the problem before tear down as the running engine will tell a better story than a dead one.

DOM