Oil out of sparkplugs?

T-Nason · Jul 24, 2023

Bought this little TO-20 awhile ago and while using it recently it seemed to develop a oil leak out of the spark plugs? I pulled all 4 and they were very much coated in black carbon. I replaced all 4 after making sure the plug holes were clean and they continue to weep. I did a compression check and got 90-90-85-80 psi. I did a oil compression test and got roughly the same psi. Seems like its a head issue? Any ideas gentlemen?

rustred · Jul 24, 2023

does the engine burn oil? plus post them plug pictures.

T-Nason · Jul 24, 2023

It wasnt burning oil that I could tell. Of course I only used it about a 12 hours total.

rustred · Jul 24, 2023

is that oil or gas? and are them plugs tight?

sotxbill · Jul 24, 2023

DO.. you have the correct plugs... ie the sealing rings type or the bevel type... the plugs MUST match the head that they are installed on. And.. are they tight enough to seal?? If you got 90 lbs on a compression test, you will get 70 lbs with a leaky plug.

INstall the plugs,, spray some starter fluid, or carb cleaner on them to clean them at the head... They should stay clean unless the valve cover is leaking or the plugs are leaking. Should not have oil coming out of the plug hole.

Fritz Maurer · Jul 24, 2023

Looks like the push rod tubes are leaking.

Janicholson · Jul 24, 2023

The head is cold, the plugs are not sealing well and as combustion gasses get blown into the threads, the oil vapor condenses and shows up as a leak. It may be using some oil, those readings are not great. How accurate is the gauge you used. And was the throttle wide open, all plugs out, battery charged, and at least 6 full compression strokes used uniformly for each cylinder? Jim

Duner Wi · Jul 24, 2023

As has been said, quite likely the tubes. Clean them up and watch carefully.

Duner Wi · Jul 24, 2023

As has beeen said, quite likely the tubes. Clean tehm up and watch carefully.

rustred · Jul 24, 2023

That makes sense to me. And should be obvious if he wipes each one down and watches them

redforlife · Jul 24, 2023

I doubt that oil is coming from out the plugs. It might appear that way. But check it out further.

For number one, most oil bypassing the rings (if so), would be burnt rather than pushed out through the plug threads. It would take a dead cylinder for oil to build up and then be pushed out. And if you got one or more dead cylinders, this thing would really be running like crap.

r.w.b. · Jul 25, 2023

that head is lot like 1 on vac case. i need to fix 1 of my vac heads.
1 must remove all pushrods ,get a big punch no burrs on it that about half of punch will fit in the pushrod holes. get a B.F.H. and maul those tubes a couple good thumps n swell tubes a tad. dont hit it like death but a couple good thumps should do it.
install pushrods n set rocker arm clearence according to owners manual,new valve cover gasket n you should be good to go

Oil out of sparkplugs?

T-Nason

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rustred

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T-Nason

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rustred

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sotxbill

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Fritz Maurer

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Janicholson

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Duner Wi

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Duner Wi

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rustred

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redforlife

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r.w.b.

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