Champion X and Champion 31: What's the Difference?

[Jerry VanOoteghem]

Cleaning and regapping plugs for my T and noticed that they're Champion 31 plugs. They look the same as the "X" plugs, but I assume they're not. Anyone know how or why they're different?

[CudaMan]

The heat range is probably different. Here is a Champion cross reference chart that includes their 1/2 inch pipe thread plugs, but doesn't show where the X falls in the heat range list.

[Tadpole]

I think there was an older thread regarding this same question, so I might be repeating someone else. 31’s are a colder plug than original X’s, although the X’s that have been being made for some time now are more similar in regard to electrode design and heat range to those 31’s. Compare the electrodes, how much is sticking out of the end of the insulator? More electrode farther away from the collar of the plug means less heat-dissipation leading to a hotter burning plug.

[Tadpole]

Lots of variations of 1/2” thread Champions, even among the “X”

[Jerry VanOoteghem]

Heat range difference makes sense. The 31's have very little electrode protruding from the porcelain. They have run great however, colder or not.

[Manuel]

The heat range is probably different. Here is a Champion cross reference chart that includes their 1/2 inch pipe thread plugs, but doesn't show where the X falls in the heat range list.

Never heard of 3/4 and 1 1/8 pipe thread plugs. I think I am reading the chart right (It is a little blurry on my screen)
Any idea what engines used them?

Manuel in Oz

[CudaMan]

No idea, sorry.

[Kerry]

Some Tractors and a few stationary engines.

[CudaMan]

Not precisely on topic, but it's been a while since these were posted. The HCCA was handing out large size hardcopies of these a few years ago at Hershey.

[Roger Byrne]

I posted a question about a Champion #30 a while back. I'm not sure what a #31 is, but below is what a #30 looks like. The electrode length past the end of the insulator is the same length as the old style Brass Top X's that I checked. I'd guess they would be the same heat range as the X. I've installed a set of them in one of my T's. They don't protrude as far into the combustion chamber as an X, but they seem to work just fine with no problems.