One of the spark plugs hisses under compression. What is the proper fix? It looks like paint and corrosion. I was thinking about using a bit of lapping compound to smooth it out.
Thanks in advance
No serious problem, I think - the pistons also leaks some under compression. But you can try wrapping the spark plug's threads with some aluminum foil, then screwing it in tight. You can also try another spark plug - I've read some repro Champion X plugs were made with bad threads.
Thread tape or thread paste, with some copper slip work well also. Just leave the bottom most threads exposed to make a good contact with the head.
Hope this helps
Actually, contact with the head isn't critical either since it's high voltage - a bad ground in the threads will act like the spark intensifiers sold as accessories back in the day http://www.mtfca.com/discus/messages/118802/169396.html?1289264982
Lets hope the coils are good and strong then. Mine were iffy at best for a long time, so I made sure of good contact.
Learned something new about the amazing Model T today.. Thanks Roger
Where is the leak? Where the plug screws into the head? Or between the porcelain and the metal plug body?
Teflon tape, yellow or white will work, couple of wraps. The threads will cut through and make contact with the head. You could also try anti-seize compound. 1/2 inch pipe tap run lightly into the hole just to clean the threads not to cut new ones might help.
If you use a pipe tap; DO NOT, I REPEAT; do not run the tap all the way through the head threads, just the tap part of the threads. The reason is, the spark plug thread in the head is tapered and by running the tap through you will destroy the taper. I found this out by mistake.