g741.org

Working on getting my ‘62 M37 going, I went to replace the plugs and the ones that the guy gave me when I bought the truck are way too big. What is the correct plug for an M37? These are the waterproof type plugs.

Plugs are 14mm.

The stock waterproof plug is an Autolite AR5S (alternate number is 2243), which is a cold range plug. These were also available as AR4S / 2242 (colder), AR6S / 2244 (cold/medium), and AR7S / 2245 (medium temp).

Champion, and possibly other manufacturers, made similar waterproof substitute plugs.

Since the originals were discontinued several years ago, they can be harder to find, especially at a reasonable price. They were reproduced, but I recall that those have been problematic. A search here will reveal more.

I wonder what the larger size was for? I guess maybe a bigger vehicle? Or an earlier vehicle. The thread size reminds me of the plugs that fit my old Farmall tractor. I will be putting these ip for sale on ebay. I have to recoop some of the money to pay for the new ones ($192 plus shipping)!

The number of this plug is 2225. Thread size is 18mm