Late 1937/Early 1938 Indian Spark Plug Question

[motor-officer]

I recently picked up several unique Edison "Indian C" spark plugs. The reason I say unique, is that they are about half the size of a "normal" spark plug. I was told they were used for a short time in 1937/38 Indians with a special adaptor. Can anybody tell me if this is correct and happen to have any photos of the adaptor? Any help would be appreciated.
Thank you.

[39ChiefBonnie]

I believe this is correct. Do you still have them?

[FLFD7]

Some photos with the adaptor….

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[PRG]

Howdy chaps,

Reminds me decades ago one could forgo the rebuild on that smokey old oil burner by soldiering on a few more miles with spark plug extenders. In the case of Indian v twins they didn’t have to reach the decrepit state of your average Studebaker to require them as the former runs a highly pressurized crankcase to facilitate engine lubrication partially explaining why they have 4 ring pistons. As Indian, and flatheads in general, are hard on top ends one might speculate the short reach J6’s in late model Chiefs from new were fitted to eek out a few more miles before overhaul while at the same time combatting overly rich mixtures, especially on choked cold starts, without fouling. Carefully assemble a top end fitted with modern pressure based 3 ring pistons and plugs such as NGK BP E7 extended tips can be fitted truly waking up these old motors which will run cleaner as well.

[RichO]

Peter would you please email me at drsprocket@att.net as I need to converse with you. Rich