Oil in intake runners

[jwgreen]

Hi all,

Been having an issue with a freshly rebuilt sbc 350 smoking. Thought it might be that the rings have just not seated as it doesn't have many miles on it yet but it was just smoking too much for me to believe that. So I talked to the shop that rebuilt the engine and they believed it was the intake manifold gasket. So I pulled the intake off and the intake runners are really oily inside the heads as well as inside the intake manifold. It does have one pcv valve coming from one of the valve covers to the vacuum port. But it was smoking just the same before this was installed.

So my question is could the intake manifold be cracked somewhere to allow the oil to be sucked up into the manifold?? All runners are about the same level of oily so it seems pretty evenly distributed. Or would a gasket leak really cause all the runners to be oily? I'm considering replacing the intake manifold but don't want to if it really isn't necessary. Thanks in advance.

 

[1987 GMC Jimmy]

When they reassembled, how did they seal the intake? The way I do it is to use the supplied gaskets for the heads and then use a little string of RTV on the ends, but the part you’re worried about is on the heads. It may just not have sealed properly or had crappy gaskets. Is this the factory intake, and was it working fine beforehand? I find it hard to believe that it would crack in that short period of time, but maybe take it to a good auto machine shop, if you have one around you, and see if they can give it a clean bill of health. That is if the service is cheaper than getting a better, easier to install aluminum intake.

 

[nvrenuf]

Do your valve covers have baffles for the breather openings?

 

[dvdswan]

My thoughts are... Why aren't the people who rebuilt your engine taking care of this at no cost to you?

Of all the engines that I have rebuilt, any smoking from the engine was gone in the first couple of minutes of break in.

Smoking from a fresh engine can be caused by several things...
Wrong head or intake gaskets, rings not seating properly, wrong size, or installed incorrectly, bad/missing valve seals, bad PCV valve to name a few.

Rings not seating properly, you can pull the spark plugs and tell which one/s aren't seating. For rings not to seat bad honing is a big culprit.

 

[82sbshortbed]

My thoughts are... Why aren't the people who rebuilt your engine taking care of this at no cost to you?

Just what I was thinking too. I'd go back and make them fix it.

 

[jwgreen]

So this is my first rebuilt engine. I had the shop rebuild it to a long block then I put all the other parts back on. Not sure how it ran prior to rebuild as I pulled it and had it rebuilt before ever running it. The intake seemed to be a stock one but cant say for sure it if was the one that came with that particular engine

Do your valve covers have baffles for the breather openings?

Valve covers are baffled, one has a breather and one has a pcv valvle.

My thoughts are... Why aren't the people who rebuilt your engine taking care of this at no cost to you?

I only had them do the long block so I'm on the hook for accessories and such.

I used a Felpro gasket on the intake the first time. Got another set and decided to just get a new intake manifold. Hopefully this will clear up the smoking issue, if not then I will talk to the engine builder about other possible issues.

Thanks for all your input.

 

[dvdswan]

Gotcha, so pull the intake, clean it really well and check for any visible cracks. I would think if all the ports are oily then take a straight edge and check to see if the mating surface is warped. Check the head where the intake sits as well. If you have a long 18-24" metal ruler you can use the thin edge and see if a feeler gauge fits underneath the edge. Do a x pattern, corner to corner, + pattern, top, middle, and bottom of the intake face.

If everything is good, reseal the intake and take it back to the shop and let them know what you found.

 

[nvrenuf]

Did the side intake gaskets show any sign of oil leaking in?

Does the hose from the pcv valve have oil in it?

Can you post a pic of the oil in the intake runners? Are you sure it's oil in the intake? Aluminum intakes can have a gold-ish stain along the bottom of the runners from gasoline.

I'm not familiar with your engine - is there anything else connected to the intake? Just seems really unusual that you could pick up oil in ALL of the runners (unless the intake was cracked in the dead center under the plenum.

 

[idahovette]

If it's a cast iron quadrajet intake that's exactly where they crack ,right in the middle of the plenum

 

[jwgreen]

Used straight edge to check the head surfaces and as far as I could tell it all looked flat.

Did the side intake gaskets show any sign of oil leaking in?

Does the hose from the pcv valve have oil in it?

Can you post a pic of the oil in the intake runners? Are you sure it's oil in the intake? Aluminum intakes can have a gold-ish stain along the bottom of the runners from gasoline.

I'm not familiar with your engine - is there anything else connected to the intake? Just seems really unusual that you could pick up oil in ALL of the runners (unless the intake was cracked in the dead center under the plenum.

No signs of oil leakage past the gaskets that I could tell or in the pcv hose. The intake was an old cast iron intake from a stock engine. There was definitely oil in the intake runners on the of the head, when I stuffed paper towels down there to keep trash from getting in there, there was quite a bit of oil on them when I pulled them out. Only other thing connected is the vacuum line for the power brakes to the back of the carb.

I went ahead and bought a new aluminium intake and installed it yesterday. I'll finish up putting all the stuff back on there today and see if that does the trick!!! I sure hope so!!