Classic/Antique Car Repair: 1940 plymouth touring, 1940 Plymouth wiring

Question
hi Robert, i can star my 1940,  was running great, but I didn't drove for like a year, now I replace the battery, and doesn't run, y rebuild the carburetor, and still not running, when I try to run the car, the battery cables became hot" I check the cables I understand red is positive from the starter, and the black must be negative, but in this car the black cable became from the starter, so do i reverse the connections? or the solenoid it its badly? what can you tell me to do??? i will Appreciate your help
thank you very much

Answer
Hello Raymond,

6 volt Plymouths were positive ground from the early 30's to 1955. While the cable colors normally are red for power and black for ground, this is not an absolute if someone has installed them incorrectly which it sounds like here.  Based upon your description, the red should go from the positive battery terminal to ground and the black to the starter.

Your battery cables could have become hot due to wrong polarity but also from a short circuit in the rest of the system or if the diameter of the battery cables are too small. The 12 Volt cables you normally find at the auto store are about 50% of the conductor diameter you need for a 6 volt system.

Before trying to start the car again, get the battery polarity right obviously but also check the rest of the wiring on the car, particularly if it's the original fabric insulated type. This insulation type of wiring can deteriorate and fall away, causing a dead short if it touches metal and can cause the warm battery cables you noted.

Just go through the car methodically and replace/repair any wiring that seems suspect.

Good luck getting this great car started!

Bob