Reply To: Martin “60” spark plug

[JOSEPH BRINCAT]

J-8  , designates the “8” is the heat range. The modern designation is J8 C  , The “C” a Champion marketing thing supposedly to designate a copper core?? If you look in vintage references for spark plugs you will often find  a suffix of “J”  , as in J8J … the “J”  was a OMC initiated designation for plugs meant specifically for outboards. The “J” indicated a plug with a shortened ground electrode. The ground electrode is shortened such that it extends only half way across the face of the positive electrode, this supposedly to minimize the chance of a carbon particle getting stuck in the gap and shorting out the plug.

As for heat ranges ;  with Champion plugs the higher the number that hotter the plug. It’s the opposite with NGK

Joe B