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Technical 7volt to 12volt changeover

Discussion in 'The Hokey Ass Message Board' started by SmallTown, Jan 18, 2016.

  1. SmallTown
    Joined: Aug 12, 2012
    Posts: 13

    from Hemet

    I have a 51 Buick Special with the original straight 8. It was quite a mess of wires and chaos when I got it. After cleaning it up I noticed that it had an alternator bolted in place, but not connected to anything so I bought a 12 volt battery for it. I got it to crank over and things are going well, but I'm starting to get nervous about the electrical. So, two questions.
    1. Besides the disconnected alternator what else do I look for to see if this car has been changed over to 12 volt?
    2. Unless I'm adding new electronics, 12 volt or 6 volt? Is there a performance issue?
  2. Flat Six Fix
    Joined: Feb 6, 2010
    Posts: 1,235

    Flat Six Fix

    Look for light bulb changes, headlights etc.
    The ignition coil, is it a 12 volt type, or is there a ballast resistor in line?
    Heater/blower motor, is there a huge a voltage dropper wired to the power going to it?
    Same with wiper motor, unless they are vacuum?
    Gas gauge voltage dropper?
    That about sums things up.
    There is nothing wrong with a 6 volt system, as long as all the connections are clean, good grounds, heavier wire for the amperage load, and nice thick 2/0 battery cables, good to go...
  3. SmallTown
    Joined: Aug 12, 2012
    Posts: 13

    from Hemet

    Thanks! This checkoff list is exactly what I was hoping for. Back to the garage...
  4. BJR
    Joined: Mar 11, 2005
    Posts: 6,749


    Don't forget the voltage drop for the radio. Temp and oil pressure are all mechanical so no problem there. Wipers are vacuum unless changed by someone. Horn and starter will work fine on 12 volt, but may need to change the horn relay and possibly the starter relay to a 12 volt one.

  5. 27troadster
    Joined: Mar 14, 2013
    Posts: 105


    Starting and headlights.

    I've run several 6V starters on 12V, and the engine is much easier to start! However, as the age of the pieces and parts we're playing with get older, the insulation of the armature and stator windings starts to break down. So you may have issues due to insulation break down, but a rebuilt 6V starter will run on 12V for years.

    Headlights: 6V suck (in my opinion) you should have sealed beam, right? if not halogen bulbs, I've heard the halogen bulbs can cause the old lenses to crack due to heat, but I don't have personal experience with this.

    Things that need 6V: in addition to the items mentioned in the above posts; the fuel gage. My dad use to run these adjustable rheostats for things that needed 6V. Haven't seen them in years, but I'm sure someone still makes them.

    Actually, if you want to hear something really crazy: Dad use to run a center tapped 12V battery on his '39 Ply. He would custom order a 12V battery with a center tap. 70's though late 80's. The alternator, starter, and after market radio (new in '73) ran off 12V, everything else ran off the center tapped 6V. It worked OK, but after a month or two of daily driving, the 1st 3 cells (the 6V portion) would go dead and the alternator would not charge them, so we would connect a 6V battery charger to the first 3 cells on a regular basis. I'm not sure why this happened, must be some quirk with lead-acid batteries I guess.

    Also, if you want it to look original, I've used early '60s Ford 12V generators. They have the same bolt pattern as some early Ply (therefore, perhaps Buick?) generators. I believe they go through '64 and are readily available. Plus I like the headlights dimming at stop lights, a small but very cool blast from the past, like slightly grinding the reverse gear at "Al's" hamburger stand, just say'n

    Hope this helps,

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