@CBoz

The difference between regular and "commercial" plugs

CBoz · 2015-11-30T20:48:46.000Z

The specs for my 1938 Lincoln K call for Champion 7 plugs. Champion 7 COM ("commercial") plugs seem much more common and cheaper, so I was curious as to what the difference was. As you can see in the first pic below, they look virtually identical. The one noticeable difference is that the COM plug has much beefier electrodes. While this might cause the spark to be *slightly* deeper in the cylinder, I can't imagine it making much difference other than a longer spark plug life. It would seem that the COM would be the better plug; am I missing something?

Nov 30, 2015 (edited)1.2K views

Replies (2)

· Dec 1, 2015

Hi,

The letters COM on Champion 7COM may not necessarily mean "commercial". I would ask Champion what it does actually mean.

I know on other plugs like J8C the C stands for copper electrode. The COM designation could be copper electrode ++?

If COM is a "commercial plug" it may be designed for a slow running engine, ie a stationary engine that plods along at 500-1000RPM, in which case it could break down under sustained higher RPM.

I tried looking up the COM designation to no avail. Wrong plugs can lead to overheating an engine or failure to burn fuel properly.

Best regards

Viv.

(edited)

· Dec 1, 2015

Thanks for the follow-up; I should have mentioned that the box does say "commercial" on it. I was thinking it would be a cooler plug, but the dimensions don't suggest that. Obviously I'll be doing more research before I stick them in my engine.

(edited)

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