spark plug question

[sidhartha]

I am running the cheaper Champion (go car) plugs in my 31 Tudor. I would like to put brass thumb nuts on the plugs to make them look more like the 3X plugs. I have found brass thumb nuts, but not the right thread size. I know the pitch is 36 TPI but I am not sure of the diameter of the shaft at the top of the plug. Without any kind of calipers I can only guess at the size. I am wondering if anyone knows what the correct tap size would be to retap the thumb screw.
Thanks Lonny

[Drive Shaft Dave]

I did to my spark plugs what you want to do to yours, give me a day or two and i will find the size of tap you need.

[Mike V. Florida]

The ones I bought from the vendors worked right out of the package?

[Joe K]

Originally Posted by sidhartha

I am running the cheaper Champion (go car) plugs in my 31 Tudor. I would like to put brass thumb nuts on the plugs to make them look more like the 3X plugs. I have found brass thumb nuts, but not the right thread size. I know the pitch is 36 TPI but I am not sure of the diameter of the shaft at the top of the plug. Without any kind of calipers I can only guess at the size. I am wondering if anyone knows what the correct tap size would be to retap the thumb screw.
Thanks Lonny

Where you get that 36tpi?

I think it is the Motorcraft plugs that are metric and you need to take an english thumbnut and tap it out a bit larger to metric thread.

I believe Champions are still made in this country (or at least made to the former english standards) So I'm surprised you can't find a thumbnut at the local Orange Place or even NAPA. Thread should be 8-32?

Anyway, it should be a small matter to bring the spark plug to the Orange place and use their parts drawers to find a nut that fits. The rest is plain, of course.

I didn't care for the go car Champions. Too tall and make the engine look like a tractor. The only problem with the Motorcrafts that I have noticed is the bluing on the base tends to rust easily. Both seem to run the same on my standard compression engine.

Joe K

[sidhartha]

A quick trip to the garage and I find that I am mistaken. Joe K is correct. I am running Motorcraft plugs and not Champions. It was Champions that I took out of the car. The Devil is in the details. So the question is what is the metric tap that will do the job? The tap should be ?mm-36.

[Joe K]

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Not sure exactly (car is in NH and I'm in FL) but it looks like the Motorcrafts might be 0.4 x 0.7mm.

See http://www.mtfca.com/discus/messages...tml?1336847770 for Model T information along these lines.

Edit: Brillman calls these M-4 threads. He sells the TT10 plugs but doesn't have metric threaded thumbnuts. Only plain snap tops.

Joe K

Last edit for tonight. See http://www.newmantools.com/taps/tapsmetric.htm for a 4.00mm diameter x .70mm pitch tap.

[Mike V. Florida]

Originally Posted by sidhartha

A quick trip to the garage and I find that I am mistaken. Joe K is correct. I am running Motorcraft plugs and not Champions. It was Champions that I took out of the car. The Devil is in the details. So the question is what is the metric tap that will do the job? The tap should be ?mm-36.

That makes all the difference in the world!!!

[raprice]

I've been using the Champion W-16Y in my '30 Model A and am very pleased with their performance. They also sort of look like the 3X.
Rog

[c. sefton]

Just bought 2 packs of spark plug nuts at Kalamazoo, motorcrafts are metric thread
(A-5) part # on package A-12409 (A-5)