I recently purchased a 1951 Lincoln Cosmopolitan with the 337. It runs but was missing on cylinder #3. Checked pressure and each was at 110 lbs, except #3 which had 90 lbs. replaced the spark plugs and it ran great on all 8. The only problem was that it began leaking a bit of oil from what looked like the middle of the exhaust manifold where the exhaust from #3 comes out. The cylinder head is dry. Any ideas? The car sat for 40 years and only has 64k miles.
Does it smoke?, make funny sounds?are all of the fluids staying where they belong and not co mingling?
Could it be spilled oil, or dripping down from somewhere? There should be no oil in an exhaust manifold to leak out. Do you mean the leak is near the place where the manifold bolts to the block? If oil pressure is good, compression is good, no funny noises, I would drive it but check the oil regularly and keep an eye on the leak. Chances are it is nothing. If it dries up fine. If it stays wet you may want to clean it off with brake kleen spray and inspect the area carefully to see exactly where it is leaking.
The oil is coming from the bottom of the manifold where it bolts to the block. Could it be a crack in the block? Oil pressure is good, but the compression in #3 is only 90 pounds, but it stays at 90 pounds and doesn’t decrease over time like I would expect from a leak.
The plugs I took out were all old and different kinds. The guy who sold me the car had done a lot of work to get it running. New gas tank, carb, electric fuel pump, etc. Those plugs are easy to replace, so I’m worried this will be a major problem.
Pull #3 plug and see if it is oily. This is not a cracked block. But might be stuck or worn rings. Lots of mechanic in a can products claim to free up rings, Try that and give it some time to free up.
Richfox is right. If oil is truly leaking out of the exhaust manifold the spark plug should be soaked and the plug not firing. Even if oil is coming out of the cylinder the manifold joint should be oil tight. I have seen a lot of oil burning engines, none had oil dripping out of the exhaust manifold. Smoke out the tail pipe, yes, black grease inside the tail pipe, yes, but not dripping out the manifold.
There is a possibility that the previous owner put oil in that cylinder to free it when he was working on it. If so you may be seeing left over oil that will dry up shortly. You might ask him what he did.
Sometimes, in my experience anyway, engines that have been sitting a long time will have what appear to be stuck rings in a cylinder or two, and running the engine will free them up, with compression readings returning to normal. A good look with a borescope helps me to see if the cylinder is scored or pitted, if I see either of those conditions I don't try to "heal" things by running the engine, if it is a motor I want to rebuild.
When you were trying to start it was it ever flooded? If it was it could be fuel that reacted with carbon kind of like wet stacking in diesels. No one has ask if you put oil in #3 to see if compression came up to check ring seal.
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