This will sound stupid, but I've been reading about chevy alternators so much it's got me confused....ha. I have a 69 camaro w/ a SBC 406, MSD 6AL and one electric cooling fan. I've read about single wire and 3 wire. My stock alternator was working fine, but this 406 is a new engine. Do I already have a 3 wire stock or should I switch to a single wire? I had a single wire on my last car and it worked great. I want to keep stock dash lights..ect.

There is just too much reading on this, isn't there?

For the most part, I don't like 1 wire alternators, and I won't talk about them.

There are 3 different 3 wire alternator types:

"STOCK" I think this is a 10SI, it uses an EXTERNAL regulator, located under the horn relay. "original" alternators were either 37 amps or 61 amps. There is a stamping on the top of the alternator idendifying the current rating and production date.

I've seen aftermarket "stock" alternators up to 100 amps.

The stock regulator is mechanical, it works with resisters and relays. A great replacement is a Wells VR715, an electronic regulator available at autozone.

Next is the 12SI. This is the '70's style internal regulator alternator. It look just like the stock one except for the small connector, whicxh has it's terminals end to end -- rather than the stockers side by side ||. This alternator is available in a bunch of factory and aftermarket configurations, including very high current ratings.

Last is the CS130. This is a late model alternator. It's bigger, and looks different, more rounded. It has a different connector with more wires, tho we still just use 3. These alternators have very high current ratings, and they put out a lot of power at low rpm's.

All (except the one wire) support the GEN light.

Which style to use is really personal preference. A 100 amp 10si and wells reg will support nearly anything you can stuff into a firstgen.

But how many amps do you need?

My own take on this is "can it keep the battery charged?"
"Will she always crank over and fire right up?"
I really don't care if the voltage drops near 12 at idle. Even my 93 vette wags it's voltmeter in time with the turn signals, though the huge CS130 in my 04 truck does not.

A "full load" with a pair of huge electric fans, big electric fuel pump, A/C on, monster headlights, and a thumpin stereo might need the idle output of a CS130. Most of us don't.

What Jim says above...
My stock alternator was working fine,
Why fix what is not broke
try it...
Stop the engine from fireing, turn on the lights etc, and turn over the enigine a fewc times or 10 sec s
Then Fire the engine
have the fan running, turn on the lights etc as if you are driving at night in the rain
Check the voltage at a couple 100 rpm above idle if it ok then the alternator is big enough

I like the " 12SI. This is the '70's style internal regulator alternator"

I realize this thread is a little old but does it matter what amps the alternator outputs as far as voltage regulator goes? I dont know what the amperage of my alternator is but it is definately a 10SI style. Can I just grab the autozone VR715 and it will work or do I need to know the output? Thanks

The alternator output does not go thru the regulator, so it doesn't affect it at all. The regulator just (tries to) maintain the proper output voltage by controlling the voltage to the alternators field windings.

Yes, you can just grab a VR715 and plug it in. Make sure it gets a good ground. 69's ground thru the mounting bolts, 67-68 had a separate ground wire.

Your alternator, if it is a facory delco, will have a stamping, it faces up, kinda aligned with the boss where the adjusting strap bolts on, toward the back on the "skinny part" The stamping will include 2 numbers followed by the letter "A" as in 37A or 61A.

Thanks Jim!! I really appreciate it!