Too much alternator?

The 49 Chevy with a newly rebuilt 235 has been changed over to 12v and I'm pulling all new wires using a Rebel Wire kit. It will have AC, HEI, dual Carbs, and at some time probably some form of CD/ipod head/amp.

The alternator on the car is shot...it is a 63 amp 10si. I'm looking to replace with a 12si. Is it possible to run too much alternator? My choices are 78 amp or 94 amp.

 

I have been running a 160 amp on my daily for 7 years. it's a big, ugly g.m. diesel monstrosity with an even uglier bracket. I had it configured to 1 wire, and I run a 4 1/2 inch moroso pulley.

at 3000, it is charging at 16 volts.

I haven't had a problem yet. My headlights are really, really bright, and the horn (if it decides to work that day) is freakishly loud.

Those are about the only side effects I have noticed. It killed a vhatoZone batery Early on (there's a shocker-punariffic!) But I threw an Optima in it, and that was that.

oh yeah. The cigar lighter could be used asd an alternate source of light and heat in the event the sun burns out.

 

Consider stepping up to a CS alternator, the late 80s truck version uses opposed mounting ears and should work with your brackets. The difference is improved idle/low speed output, which you'll appreciate with AC and a sound system. Here's a good link about em, only adds a couple bucks to what you already planned to spend.

http://www.novaresource.org/alternator.htm

 

Technically, you probably can't run too much alternator. Whether you have a 78 amp or a 200 amp alternator, the alternator is only going to output what the current electrical demands are. For instance, even if the alternator is turning 2500 rpms, if you basically have nothing electrical on, other than the engine ignition demands, the alternator is probably putting out 15-20 amps. As you turn on additional electrical demands, such as wipers, AC, stereo, electric fan, the alternator will increase the amperage output as each of these items is turned on. And as each item is turned off, the alternator amperage will decrease.

I agree with Shifty, the CS alternators are newer and better, especially the low idle output as Shifty mentioned, but they also have an additional internal fan in the rear to help keep the diodes and rectifers cooler. The 10si and 12si's are being rebuild for the higher 100 amp range, but they only have the external cooling fan at the pulley to help combat the internal electrical heat.

But to answer your question, if you wanted to run the 94 amp 12si, it wouldn't be a problem.

 

The best way I have found to know what you need for an alternator, when you are building a car, is to use the method that the OE engineers use. The first step is to find your total amp load of all accessories that would be on at the same time on any given day. The engineers have charts for this, we don't. Get yourself an amp meter with an amp clamp. Put the amp clamp on a battery cable. Power up the meter. Turn everything on that would be running constant. DO NOT HAVE THE ENGINE RUNNING! Turn headlights, taillights, step on the brake, heater, defroster, wipers, engine cooling fan, A/C compressor, car stereo, etc. Record the amp draw you have from your battery. Do not be concerned about momentary draws such as power windows or power seat, etc. they will be figured in later. That reading could be as high as 50 amps, so do not be shocked. Now, add 20 to 25 more amps to that reading. This is for the momentary draws, the ignition module draw, and for extra charging of the battery. Your alternator must be at least this big in amps. Bigger will not hurt you, but engineers do not want to waste energy, weight, and cost to the vehicle.
As said earlier, if you are just building your car, try and engineer a CS type alternator, they are better. The more you draw from an alternator, the more heat is wasted. The new CS alternators have internal cooling fans and will last a lot longer. When they build up the older SI alternators, the heat is unmanagable and the alternator will fail early.
Here is a little interesting tidbit concerning alternators. A 100 amp alternator putting out full load (60-70 amps) will draw 5 HP from the engine. 2HP is lost to heat, wasted energy, 1 HP is lost to air friction of driving the cooling fans. The remaining 2 HP is what you actually got to produce the amps you used, so, the alternator is actually about 40% efficient. All that information won't do you any good, but it might get you a win in a trivia game.
Good luck in your project.
Street Rod Steve