MTFCA Forum

I know the discussion has gone on as long as there have been Model T cars. Here are two new old stock unused Champion X cores I just bought (at a discounted price from what they were asking) that have the ribbed top and the old style small nut ( I believe) which should be 5-40 threads. Common or not to have that combination ? Lot's of discussion in the past I believe , I ordered a 5-40 tap and I will re-tap 4-40 Brass Knurled nuts for these, as 5-40 seem to cost an arm and a leg if you can find them . Anyone else re-tap 4-40 Brass knurled nuts to 5-40 threads ? I see no reason why that will not work. The copper colored gasket is , I believe, the top gasket as these have two gaskets, unlike the newer type. I will be trying the copper crush gaskets with asbestos substitute from the aviation supply. The gaskets are 1/2 " I.D. X 3/4" O.D. . I will make a brass upper gasket from thin sheet brass using my gasket / washer punch set .

Anyone else re-tap 4-40 Brass knurled nuts to 5-40 threads ?

Yes, I have. They work fine.

4-40 tapped to 5-40



I believe those ribbed take-apart cores are from about 1921 or 1922. They're not exactly rare, but they're less plentiful than the brass hat plugs that were used during the years of peak model T production.

Last of the take-apart X's.

Thank you for that information Jeff......good stuff ! To your knowledge, has anyone tried to reproduce the center electrode ?

Not to change topics, but I thought I would put this here....a Champion #32 for a METZ , taken off of that auction site. I imagine this would put a very large hole somewhere when a Model T piston would hit it , if you were to try it (NOTE: Bad idea I think )

Hey Dan....., that was a great post on those Champion X take aparts. Few years ago I did purchase some of those cores and used them a little while later only to find out that what I bought wasn't exactly usable. For some odd reason there was no continuity between the top terminal and center electrode. If there's no continuity , that spark plug will not spark as it should.

...has anyone tried to reproduce the center electrode ?

I doubt it. I think that's a DIY project.

Moxie26 wrote: ↑

Tue Oct 25, 2022 8:24 am

Hey Dan....., that was a great post on those Champion X take aparts. Few years ago I did purchase some of those cores and used them a little while later only to find out that what I bought wasn't exactly usable. For some odd reason there was no continuity between the top terminal and center electrode. If there's no continuity , that spark plug will not spark as it should.

That's really odd.....they were the take apart kind you can take the center electrode out ? No cracks? That's a real strange one ......I wonder if it was weak spark , bad wires excessive resistance ? I'm running 6 volts but with a distributor , so I have no experience w/ stock model T ignition . I imagine if you had faulty porcelain it could go to ground .....

The cores I purchased were the ones with the brass cap, later manufacture, not the ones that you can take apart.

Moxie26 wrote: ↑

Tue Oct 25, 2022 4:15 pm

The cores I purchased were the ones with the brass cap, later manufacture, not the ones that you can take apart.

Were you ever to determine what the issue was ?

I still have those defective cores. Being that they're manufactured as "one piece sealed units" there has to be a break in between the top terminal and the center contact .

Moxie26 wrote: ↑

Tue Oct 25, 2022 4:24 pm

I still have those defective cores. Being that they're manufactured as "one piece sealed units" there has to be a break in between the top terminal and the center contact .

I guess that is the only thing it could be , short of some impurity in the metal having to much resistance ....that is a strange one .