Did a word search here and found several strings addressing this issue.
What a great resource this FORUM is!
(I hate bothering my "go-to" guy with this tiny ticky s--t.)
Anti-seize, aluminum foil and (my choice) Teflon pipe tape.
I wonder about the Teflon tape melting. Apparently it does not.
Permatex makes a high temp sealant for this purpose. I've used it on one of my engines for several years now with good results.
John, take a look at the threads on the plug, some times they are double cut and you will never stop that leak.
Teflon tape is an electrical insulator.....
I'd go with the Permatex rather than the tape, for the reason Greg stated.
I have never had an issue with Teflon tape. The threads cut through and there is plenty of metal to metal contact.
I use high pressure, hi temp pipe sealant.
Ken... You still have that old "red beater" I last saw you in? ;) Kidding of course.
I have Teflon tape and Permatex but I'll check the threads out carefully before I go. I like the sound of the Permatex solution so I think I'll go with that. Let you know how it goes.
Thanks all and Merry Christmas (I'm not a believer in politically correct "PC" or happy holidays)
I always oil the threads when I install the plugs and I see a little bubbling at the oil on the threads when the engine is running. I decided to ignore the tiny leaks since there seems to be no harm done by the condition. Am I wrong, and can there be erosion of the head's threads (or other unexpected adverse affects) due to tiny leaks over time?
Got to agree with Mark....I have never had an issue with the teflon tape.
You are right, there is no reason to fret over tiny leaks. Pipe thread is not ideal for spark plugs, which is why you don't see pipe thread on today's car engines. Nonetheless, it works fine on a Model T, and the slight leakage doesn't make any difference in performance or reliability. It's just part of owning a car designed 106 years ago.
I put Nickel Eze on spark plug threads because it prevents corrosion and promotes conductivity.
If it's just a small leak, which is typical - ignore it, it won't hurt anything.
"Small" or "large" are very subjective. It leaks and it should not.
My thought was since these are already low compression engines the plugs need to be sealed to ensure you have the necessary vacuum (correct?) to get gas to the cylinder.
If I could add a comment - are you sure the leak is coming from the plug. I had one that upon close check was actually a small place on the head right above the plug that was oozing water to the top of the head. Looked like a place had weakened over the years and made a small pin hole. Found some J B Weld that works with water leaks and it stopped it. Just a thought - maybe someone else had this experience.
Teflon tape works great for me. If you have so much tape to cause an electrical insulation problem, you have another problem that needs to be dealt with. JMHO. Dave
As it is used on frying pans, teflon won't melt at the operating temperature of a Model T engine, however, standard white plumber's teflon tape, which is used to stop water leaks, will not stand up to gasoline, so, in this application, where gasoline is present and under pressure, as a vapor, just prior to combustion, I would use yellow teflon tape, which is not dissolved by gasoline. Jim Patrick
Unless the threads in the head are really shot, you can usually just drive it and they will seal up good in a couple hundred miles (a days ride).
If your rings are worn, and your engine "pumps oil" they likely will never seal up and you will have a bubbling ring of wet oil in that little valley forever.
A friend of mine used the yellow PTFE paste on his several years ago and it seemed to work just fine.
I had a badly rusted "T" head pipe thread and I used resin. Coated the thread screwed it in and let it set up and sealed good, also not impossible to get out.
Get a standard 1/2 inch pipe tap and clean up the threads.
Usually a turn or two will make them all look like new and they will not leak.
Thanks folks. This in the 1915 engine I just got running (again) today.
Now... back to the plugs! Lots of opinions, all valid. I'll have to give some thought to it.
John, If you chase the threads with a pipe tap, don't run it all the way through the head the hole is tapered and you will end up sealing all the time. I learned this by mistake. I use gas pump thread sealer, like the repairmen use on gas pumps at your local station. I check the seal, by starting the engine and squirt oil from my oil can I use for the chassis to check for bubbling. I learned the tap problem from an old T guy.