MTFCA Forum

Took the 22 out for some test driving today, working on my shifting. Stopped for a minute when I noticed a fuel smell that seemed pretty strong. Gas cap had a decent amount of gas on it, I assume from the little breather hole in it. But I also checked the engine and noticed that it was wet under the #2 spark plug. Heart kind of sank a little. Is this an easy fix or am I looking at pulling the engine and pistons?

About the gas tank Most likely filled to the top when it was cold and as it got warmer the gas expanded and ran out. Or you went up a steep hill and some came out. Could have even come out as you went over bumps. You can use a gasket under the cap, but you do need the small breather hole open so air can replace the void left when the gas is burnt.

If it is water around the spark plug, it could gotten there by rain through the hood hinge, or worse, by a crack in the head in that area. If it was oil or gas in that area, it would be from a leak around the spark plug threads. It can happen when you have an open throttle and the higher compression forces a little oil or unburnt fuel through. There is no gasket and the plugs have a tapered shaft so they tighten up just like water pipes. If the area is a bit corroded, you could break the plugs off if you tighten too much. I have found that a layer of aluminum foil wrapped around the threads before I tighten the plugs seems to stop that.
Norm

The gas cap leakage may be due to a gasket problem. The "wetness" around one spark plug, I am assuming, is of an oily, sooty nature. That's not uncommon, and is caused by slight compression/combustion leakage at the threads due to thread wear and perhaps the threads on the plug not being very well made. If the plug is reasonably tight and still leaks, wrapping the threads with some teflon pipe tape will usually stop it. Overtightening the plug probably will not stop the leakage and may crack the head. I used teflon tape on mine with good results, and after removing the plugs 2 or three times, I found that they now do not leak even without wrappeng them with tape each time I replace them in the head. The threads on the Champion 25 plugs look poorly made to me, with the crests of the threads largely missing. I think enough of the teflon tape embedded in the defective threads to give an effective seal. Others have used aluminum foil as thread tape with good results.

Whew, I was thinking the worst. Going to get my Teflon tape and wrap the plug threads as soon as this football game is over.

tgarron33 wrote: ↑

Sat Oct 09, 2021 3:03 pm

Whew, I was thinking the worst. Going to get my Teflon tape and wrap the plug threads as soon as this football game is over.

Teflon tape can insulate. Use some anti seize.

I have found that the threads on Model T spark plugs cut through the Teflon tape in places and grounding of the plugs is no problem. Just don’t go crazy with the tape.

The threads cut the tape or squeeze it so thin it can't effectively insulate the plugs. I tried touching the engine block and the spark plug bases with wet hands with the engine running and felt nothing.

A friend just had a similar problem after he installed some new Autolite plugs. He reinstalled some Motorcraft plugs and the problem went away. I don't know if running a tap thru the threads would help - you don't want debris falling in the hole.

I think the problem may lie with the half-baked threads on some modern plugs as much as with worn threads on the engine. A pipe thread that does not bottom ought to seal. I would not want to run a tap in cylinder head threads that are likely already worn oversize.

I have success by wrapping 2 turns of Teflon tape on the spark plug thread. No leakage anymore.
Test for leakage by pouring water into the spark plug relief then look for any air bubbles.
Art Mirtes

Oil in the wells around the plugs is usually an indication of worn valve guides. Car might also smoke a little and/or the back of the car may have a light haze of oil on it after a few hundred miles of driving. Sealing the plugs up a bit better can help. Avoid any teflon tape because bits of it can fall into the cylinder when installing & removal.

TXGOAT2 wrote: ↑

Sat Oct 09, 2021 5:37 pm

The threads cut the tape or squeeze it so thin it can't effectively insulate the plugs. I tried touching the engine block and the spark plug bases with wet hands with the engine running and felt nothing.

I tried that once. Didn't like it.

Permatex thread sealer works well if the slight leakage on the plug bothers you that much. It's what I used on the plug threads when I installed the aluminum Prus head (which is marvelous by the way). Also used it to seal a plug on a diesel fuel/water separator assembly. It's great stuff (not to be confused with THE RIGHT STUFF) for this kind of application.

Beside a little oil around the spark plug, if the threads are worn enough, you might even hear a little whistle or a chirp when pulling a hill. Caused by the combustion gas leaking out. Sealing them does fix both problems.
Norm