Dear Car Talk:
I have a restored 1947 Plymouth Business Coupe. That was the same year I, too, came off the “assembly line.”
The Plymouth has a 6-volt battery, and the starter motor turns over slowly. Can I safely install an 8-volt battery?
Will this improve my starter motor? Or, will this risk damage to my lights and instruments? Thank you. — Jerry
All of the above, Jerry.
The problem is that everything in your car is designed to run on 6 volts.
Running 8 volts through 6-volt components will put some stress on them and might shorten their lives a bit. But in truth, the lights and instruments can probably handle an extra two volts. It’s not enough extra voltage to cook them.
The bigger problem is that you have a 6-volt generator. And, a 6-volt generator will never be able to charge an 8-volt battery. So, your idea will work for about two hours.
And, you can’t simply replace the 6-volt generator with an 8-volt generator in this car, because they don’t make an 8-volt generator.
Your best option is to skip over 8 volts entirely and just jump right to 12 volts. You’ll basically convert the whole car to a 12-volt system. There are kits for this. Other old-rust-bucket enthusiasts can advise you.
You’ll need a kit that has 12-volt bulbs, a 12-volt windshield wiper motor, a 12-volt generator, a 12-volt starter motor, a 12-volt voltage regulator, etc. And you’ll probably need to replace at least some of the wiring. Fortunately, a 1947 car only had about seven wires, so that’s not a big deal.
So, 12 volts is the way to go, Jerry. That’ll solve your starter motor’s chronic fatigue syndrome and any other electrical problems you have. It’ll also solve that problem of figuring out what to do with your next 12 weekends.
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