While cleaning up my brass cap red Champion X spark plugs I came across this black lettered plug. It has no other markings on the porcelain; has anyone seen one like this before and can you tell me if it pre-dates the red ones?
Now that I see it, I'd say yes and no. It does predate the other plugs shown with it, which are a later version (crimped brass hat, ribbed insulator, 8-32 electrode thread, long base). It's an earlier plug (straight insulator, can be fully disassembled, 5-40 thread, short base). But I don't remember seeing the black label before. All mine have red. I hope somebody can tell us about it.
Maybe ask these folks?
The ones with black Champion lettering are the premium "Heavy Stone" plugs. They were made for many applications including the Model T. They were produced at the same time as the Champion X, and were available with brass tops slightly earlier than X plugs.
From a June 15, 2015 thread:
This one fits into the mix somewhere. We have had some great discussions on plugs. Maybe some ambitious sole will pull them all together some day. (Not Me.)
Your plug is Champion factory authorized plug for the Fordson Tractor.
This thread also talks about the "Champion Toledo".
As explained earlier, the Model T "Champion X" was one of the last to receive a brass top, probably to save money since millions were made every year.
The Fordson tractor started on gasoline but could be operated on either gasoline or kerosene. It likely had a colder plug to try to lessen spark knock when running on kerosene. Will it work OK in a Model T? Try it and see. Our gasoline is far better than 1909 - 1927 gas. Spark plugs and valves last a lot longer now than they did when the cars were still being used as daily drivers.