MTFCA Forum

Does the plug sit flush with the hole or does it protrude into the chamber? I am making thread repair Bushings and my old threads are worn so so it is hard to tell.


John

The plug will seat into the combustion chamber of the head, but will sit up as not all of the pipe threads on the plug are used, so the plug will stand up a ways above the pipe thread hole. This is a high head and Ford script Champion X. Other plugs may have different reach or heat range.. This view of cutaway the plug is just placed for reference, it won't actually sit this low.

Don't tap the pipe threads too deep if you are going to rethread those in the head.

Better views of plug reach, plug is Champion 25.

Thanks Dan. I figured some threads should show on top. I am tapping existing threads in a brass bushing to get the right height.It is working out good on my test head. I will mark the tap and get each one the same on my good head.

John

Even if you restrict the question to Champion X, they come in two different lengths.


Other plugs you can use on a Model T also vary in length.

some people are known to carefully wrap aluminum foil around the plug threads a few times. I haven’t.

I only use aluminum foil if the oil or combustion comes through the threaded area. If the threads are not too worn, it will seal it combustion tight.
Norm

I use ether antiseize or white teflon tape. Both seem to work fine on weepers.