M37 spark plugs

[John Mc]

Thanks for all the input. My '52 M37 (bought recently from a Fire Department) has Champion J11C plugs, no adapters, it starts and runs fine. Has a 12V system.What's the purpose of the adapters? Seems like I'm missing something..

They allow the use of standard, modern plug but make a waterproof connection and work with the rest of the truck's water proof ignition system. If you have a 12 V system, you probably no longer have the waterproof distributor with the ignition coil mounted inside, and the plug wires which accompanied it, so not much point in waterproofing the plug end of things.