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My mechanic tells me that it is okay to use a 12V positive ground battery in a 6V positive ground car
sounds fishy to me but I am not an expert
any comments appreciated
thanks
Tim

Sure if you want to burn out the courtesy lights, coil and anything else electrical and possibly to destroy the starter housing in the process. So the short answer is, yes it can be done but it requires conversion of the electrical system’s components.

As to the starters, while many do not convert anything but the solenoid and keep and use the motor as a 6v component running on 12v, they will work beautifully for a time and start the car with more speed and pep than ever when run that way -- until the one time they don't.




Finding a good Autolite or Delco starter casting is getting hard and expensive for even some of the postwar engines. If your 34 has one of the rarer brand or model starters then you could be in for a challenge and a flattened wallet if you break a casting and need a new one. Moral of the story is be sure and have your starter motor converted to 12v if you are contemplating a conversion. If you have an Owen-Dyneto starter I don't know how easily found or available 12v field coils would be.

Along this thread, what experience is there with 8V batteries? I know they have been used in 6V systems over the years but I have no experience with them nor do I know anyone who uses them. I did talk to a fellow enthusiast at a car show earlier this summer who has one in his '37 Cadillac and likes the stronger hot start he gets with the extra 2 volts. I asked him what about burned points, extra strain on the starter, burning out the lights etc. and he had no issues and had made no concessions to the stock wiring system.
I am still skeptical so I wanted to ask the Forum and this thread looked like the place to do so. Along this tact, is there a voltage resistor that could drop 2 volts after the starter like the ballast resistor in my newer 50-70's cars? (I remember carrying extras in the glove box of my MoPar as they seemed to go quite often!) And if so, would that prevent a full charge getting back to an 8V battery? (So many questions in life!)
Thanks for your input,
Bob J.

Quote:

He's wrong, end of story

Bob,
8 V will strain the lights, not sure it would affect a lot else. Coil could overheat. 6V systems charge at 7V so an 8V if you don't use the car's charging system, would work well enough I think.

As others on the forum have said many times, 8v is not necessary if the car is kept in tune, is mechanically in good shape, and wiring is in good condition.

Having gotten that out of the way, on old and tired or worn out cars it can help give a few more years of dependable service. When I was a new driver in the late 50s, in our part of the world 8v batteries were a common easy to do and fairly cheap "fix" for hard to start junkers where a car might be fairly old or tired and an owner didn't want to spend money to get it gone thru and fixed properly. My father was a firm believer in them and I suspect all his 6v cars and trucks were so equipped at one time or another. The 51 that I drove thru high school certainly was.

Most stock 6v bulbs and even larger components are rated 6-8v -- or can be bought that way -- so while they might have a minimally shorter life on 8v it is not a drastic thing. All other components will hold up fine and about the only change needed to the car is to adjust the regulator so it charges at about 8.5v or a bit higher instead of 7.4. I know my father did not have a meter for any precise adjustments because when he made a battery change he just went in and tweaked the regulator adjustment screw a tiny bit at a time -- just until the charge indicator or idiot light went out. It might need a touch up again if the battery seemed low after a day or so or again if the battery seemed to be losing water due to overcharging. Like I said his adjustment was real precise --NOT..

Back in those days old cars were just old cars and if he really screwed something up then he'd break down and take it to a gas station or to one of his friends, a couple of whom were official shade tree mechanics with businesses out of their garages. His newer cars he did sometimes take to a dealer if it was something serious that needed a part but even that was not a given if one of his friends though he could fix it..

Converting your '34 Packard Eight to 12 volts would be a travesty. DON'T DO IT!

Tbone-- Heed HH56 and Owen_Dyneto. Do not do it. Do not pervert a vintage car in this manner in order to circumvent slipshod work or other problems. No, no, no.

6-volt systems work like a charm given a healthy battery (many like Optima Red Top 800 cold cranking amp 6-volts), 00 (double aught) solid copper battery cables ends both crimped and soldered, correctly rebuilt or sound starter and generator (bolt-in, no butchering + ground, 55-amp alternators from Jim's Battery Manufacturing 800-426-7580 an option), good grounds and connections throughout.

Your car will work as Packard, who knew what they were doing, employing a phalanx of well-educated engineers, intended.

Well
I am glad I asked, I will have mechanic switch 12V battery to 6 V
appreciate all the helpful advice

I would also change the mechanic!