12 volt conversion 1941 coupe 1948 engine

Joe
Might be late to the party, but nowhere have I seen anyone inform you, with 6V systems, yes they are half the volts but they are TWICE the Amps of a 12V system, thus your problem is coming from the AMP side of things, not the Volt side. If your can crank your car over and feel the battery cable to the starter and its HOT, you have to small of a positive and negative cable, Especially the further the battery from the starter. MOST 6V problems stem from having 12V battery cables on a 6V system. You can go to you local welders supply company and Get 0 (ought) cable and make a proper size cable for 6V system. THEN GROUNDS, GROUNDS. Check an make sure all the proper grounds are clean (USE Di-electric grease to coat each connection) for GOOD grounding, that should solve your starting issues. ALSO check your generator/voltage regulator to make sure your system is ALSO charging properly!!!!
 
Joe,
I just finished converting my '41 coupe to 12 volts and am very happy with the results. I went the expensive route with parts; here is the breakdown:
- 12 volt battery $100.
- 3 Runtz voltage reducers for Oil, Fuel, Temp gautes at $18 each
- 2 Halogen headlights (twice the brightness), $70/pr. Some recommend installing a relay for the headlights to save the switch. But the halogen lights draw about half the current (4 amps) of the stock 6 volt lights, - so don't worry about it.
- I put in LED tail and brake lights $35 each. Easy plug and play for much more visibility to those behind you.
- 12 volt light bulbs at about $1.50 each: 2 parking, 2 instrument panel, 1 ignition, 1 high beam, one rear plate. I do not have a dome light or trunk light.
- Starter solenoid $34. You can probably get by using the originial 6 volt unit, but if it fails closed, you will regret the economy.
- Horn relay, $16. Again you can probably get by with the original, but if it sticks on, you will probably fry the horns before you can get the battery or relay power disconnected.
- Speaking of horns, I tried to cut voltagte to the horns by installing a 1 Ohm resistor in the wire to the horns. The horns did not sound and the resistor got very hot very quickly. I will try something else because the horns are much louder and lost that mellow tone.
- I put in the polished aluminum PowerGen one-wire alternator that looks similar to the original generator. It was $429, but there are much less expensive solutions. Like forego the shiny finish, or having your generator modified.
- With the one wire alternator the regulator becomes a firewall ornament. Hook the generator/alternator wire together with the battery wire to the Battery terminal on the regulator; retain the ground wire by attaching it to the alternator case; remove the Field wire altogether.
- Change to a 12 volt coil for maybe $30. If the new coil has 1.5 Ohm resistance, bypass the ignition resistor under the dash.
- The best thing I did was install a Pertronix Igniter electronic ignition ($123), with their Flamethrower coil ($35), chrome of course. With that and the hopped up starter, you can hardly get your finger off of the starter button fast enough. But Pertronix is electronic and lives in a very hot location. - So it will fail at the most inconvenient time. I carry a spare distributor and coil at all times.

My heater is shot, so when I overhaul that, I will have to convert the motor to 12v. I also still have to convert my electric wipers.

So far, I put $950 into parts. If you go economical (no LED, no halogen, no relay, no solenoid, no Pertronix, no/cheap alternator) you can do it for half of that amount.

Took me about ten hours altogether, but I am old and slow.
Good luck.
 
A 6 volt alternator after the cables and connections are checked it the best solution to make the 6 volt system better. I have 7 of my old Fords running 6 volt alternators. Charges at idle and low speeds and more amps to carry head lights in slow city driving. Plus will run the GPS on 6 + volts. With a generator my GPS would cut off in town just when I needed it from low voltage. A small 6 to 12 volt converter solved that problem when I had the generators but the alternator is better. G.M.
 
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