Champion J-3 plugs
 

Anybody know what these were used for as in application wise to look up something similar that is new? The ground electrode is inside the steel shell, not in the usual location welded to bottom flat of the threaded section.

Identical to this K-3 in the picture where they were being using in a marine application. The J-3 is probably just a difference in heat range.

Look at the fourth post with the pictures:
http://johnsoldmercurysite.com/phpBB...hp?f=17&t=4829


The J-3 plugs I have had been installed in 60HP Flathead with factory aluminum heads.