Gm 10si alternator on a mc?

[monzanick]

Anyone done this? I've had it with the 6v battery and generator. I can get 12v batteries for cheep-2-free so I'm gonna upgrade to 12v. I'm sure I can figure it out . Any pics of a gm at on a m, mc or 40?

[Stan Disbrow]

Hi,

Many have done this. Except me. I won't do this. Unless, I also had the starter windings rewound to 12 volts.

Putting 12v onto a 6v starter is pretty tough on it both electrically and mechanically. Your ring gear won't be happy and you run the risk of having to pull the engine to replace a chewed up ring gear. The worst thing is you run a risk of busting the nose cone of the starter, which you can no longer replace.

If you decide to proceed, use a small, low CCA 12v battery and run small diameter (number 4) cables. I'd use at least 12" cables on both the battery terminals - not the number 0 short cables used on the 6v system. You want to limit the current draw of the 6v starter on 12v to lessen the power and, hopefully, not kill it. Or, at least not as quickly.

Note that the smaller diameter cables will heat up. This is a good thing. You want them to act as resistors to the starter. Speaking of resistors, don't forget the one you need in the power feed to the coil.

I know other folks will chime in that they have had no problems. But, being Mr Electrical in a large antique equipment group, I can say I have seen a lot of issues with putting 12v onto a 6v starter.

Stan