What kind of spark plug system is this?

[Kneale Brownson]

This is out of the six-cylinder Wisconsin engine used in a Cletrac 40.  The collar at the top holds the ceramic section into the part at the bottom that screws into the head.



This is a closeup of the ceramic section.



This is an assembly of what's left of the plug. The ceramic top with identifications is missing on all six.  The spark tang that grounds on the head is attached to the part that screws in.

Where would I find a replacement plug?

[Bob]

That is a plug that was made to be able to be taken apart and cleaned. Replaced by modern plugs. Autolites work good. Can look up by thread size

[Blake Malkamaki]

7/8" plug. Champion W-18, though I prefer something besides Champion. Older Champions were ok - they were "1 COMM" "2 COMM" "3 COMM" depending on heat range.

[Kneale Brownson]

Found a Champion W14 that fits the threads and is about the same length.

Thanks for the replies.