Thread: Oil on intake; hard to start, backfire....

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I am finding oil to puddle in the bolt valleys of my 350 Chevy manifold. Just in the front two, both sides. Worse on driver's side. It's an aluminum manifold, with a B&M 144 Blower on it.

Also, it has started getting hard to start. I have to crank it over for a bit. Whereas it normally will start right up.

Occasionally when it does start (after having shut it off for just a few minutes, and restart, i.e. fill up with gas) it backfires very loudly...out the exhaust.

Would poor manifold seal do this? I didn't realize it would.

By the way, it seems to run fine once it's started. Doesn't exhibit symptoms of a vacuum leak. But, the backfire, slow starting, and oil puddle symptoms seem to have started pretty much at teh same time. Although, I will say that the oil puddles started first. Then I drove it 1500 miles to Colorado Good Guys and back. Didn't experience the slow start and backfire symptoms during the trip. Just the oil puddling.

Before the trip I had changed the valve cover gaskets to good quality gaskets thinking they were leaking. But the leaking didn't stop, and now the other issues.

I was thinking about pulling the manifold and resealing.

What are your thoughts?

I checked the very front ones and they were tight. But I couldn't check the next ones back. They are hex head bolts, and I can't put a tool on them w/the blower on.

I was thinking if they were loose or not sealed well, I'd have water leak up through them.

I do think I probably need to pull the manifold and put new gaskets down, but I'm just seeking thoughts before I tackle it. I'm guessing the backfire is because of the slow starting, it's loading up gas in the exhausts, and when it starts it backfires.

Has anyone experienced oil puddles on top of the manifold (front) on a 350 chevy from a not-sealed good enough manifold?

I do plan to re-seal teh manifold. But it seems strange to me to have oil puddling at the front from that.

BTW...the engine is running real good. I'd think if the manifold was not sealed good, there would be other symptoms.

I think the backfire may be from the slow starting, which I am thinking is due to a weak battery. So, gas gets pushed into the exhaust due to slow start, and when it does start, I get the backfire out the exhaust. I'll know soon on the battery. I have a new one coming.

My wifes 91 suburban has an aluminum intake. Factory stock injection. I had what I thought was oil at the bolts on the intake. I found that the oil was just a film. Antifreeze is what was leadking it had bad gaskets on both sides. I guess thats common with dissimerler metals? I changed the gaskets and it all went away. Take a paper towel and soak up the oil you will probably find it is coolant with just oil sitting on top.
Charlie

Thanks for the thoughts. I have actually done that, and it appears to be all oil. However, it is a good idea to do that again, with more scrutiny. I'll post back what I find. I can say that I do get the smell of oil once in a while when I'm driving, so I'm doubting I'm lucky enough for this to be it.

ussually ones you get anything leaking through an intake gasket, retorqueing wont get rid of the leak, the gasket will have kind of a wear channel wear the leak was and so the leak will lessen but still continue.... you'll have to replace the gaskets, use the best ones you can get too, cause the blower puts more load on them obviously

I am planning on replacing the gaskets.

This is interesting. Out of all the engines I've built (well, really, only about 6-8), I've never had this happen. I didn't realize that I could get that type of leak from the intake manifold. That is, oil on TOP of the manifold.

If you want more oil drive thay big round thing on top a little higher.
Just kidding