MTFCA Forum

Hi folks, I'm new here and a new owner of a '15 touring. My father in law restored it years ago and since he passed it has come to me.

I've been working on getting it back together, and found that spark plug hole #1 is in bad shape, the threads crumbled as I removed the plug. Also the threads on both of the holes of the water outlet ears are pretty much nonexistent, the bolts have nothing to grab. My FIL was using overlength bolts with nuts behind the water outlet ears. So to fix this properly I'd be looking at helicoils or threadserts for all 3 of these. Plug hole #1 would be a challenge to do without removing the head.

He did have a spare engine block sitting in the garage next to the T, and the head (also a low head) looks like it has good threads on all plugs and water outlet ears, so I'm leaning heavily towards just swapping the head out.

Some questions I have are:

- what else should I look for on the replacement head to make sure it is sound?
- can i reuse the gasket, or use new, copper or silicone? not sure what material the current one is
- am i ok to reuse the head bolts?
- should i be using overlength bolts anyways on the water outlet, and back them up with nuts and lock washers?
- any other tips appreciated!

thanks
MB

I would
1. Have someone check to make sure the head is flat
2. Plan on using a new copper head gasket
3. Buy new head bolts
4. Use the correct bolts on the water outlet (no need for nuts and washers)

Look for another head, they are not too hard to find or too expensive, repairs to the damage you describe would be expensive and not really satisfactory.
All the best and welcome to the hobby!

Helicoils do not work in tapered pipe threads such as the model T spark plug hole. Get a better cylinder head. Better yet buy a high compression aluminum head. The best bang for your buck on a model T.

I'll second the get a new head. However, if there is sentimental value or some other reason for keeping it you may have luck with delicious and studs for the water outlet and taping the hole deeper (tapered thread) so that you could then use an explosion whistle and then plug compensating for the deeper threads in case a plug bottoms out. Worst case you mess up a head you were going to replace anyway.

It might be possible to tap the plug hole out to a larger NPT size and then screw an all-thread pipe bushing into it to get back to the original thread size. The bushing would need to be seated tightly and staked or pinned to keep it in place, then threaded internally to the correct size for the plug.

I had a head with bad threads in it. It was a nice low head so I bored and threaded the holes to take Model A size plugs and took .125 off
of it to use on my speedster.
Works well.

Not a hard repair, done several over the years.

Neat job on the inserts - nice.

It is a cost benefit decision. Anything can be done, how much do you want to spend?
Having another head right there to use suggests go with the swap out.

Very clean fix.
If you have the capability, thats a great way to replace the threads.