The Stovebolt Site Forums The Shop Area The Electrical Bay What should I be looking for in an Alternator?

I've decided to put an end to the 50 year old wiring mess that's in my truck. My truck is running an generator and about 4 years ago I purchased a harness from Chevy Duty to switch to a GM alternator with internal regulator. I'm getting ready to break it out and rewire the whole thing. My question is what should I look for in an alternator? OK, the reason I'm asking is I know how it's going to go when I get down to my local parts store. I'm going to tell them that I need a GM Alternator 3 wire with internal regulator and their going to ask me "what's it fit?" Seriously, I go through this everytime I go there. Even it's as simple as a intake gasket for a SBC. I just make up a different application every time, knowing that what I need will fit a multitude of vehicles. They must think I have a fleet of cars! Sometimes it's a '61 Impala with power brakes or a '70 Nova with air conditioning. Hee hee hee. Anyway, back to the point...what years and applications used this alternator?

Most guys go with a 10SI or 12SI Delco because they're cheap and easy and you can even get one in chrome.
Thats the alt. GM used for years and can be had as single wire self energizing type if you want.
Any parts guy, short of a nimrod, should know what that alt.is.
Any chevy mid to late seventies would have that alt.
Dan

What's the difference between 10SI and 12SI?

Not much in physical looking outside dimensions, the 12si is heavier, about 1lb, the 10si weighs in at about 10 lbs.
The 10si was the first SI (internal regulated )alt. and has the upper adj. bolt thread 5/16x18.
The 12si came later and has higher output capabilities and better cooling to deal with under hood temps on cars of the 80's.
The upper adj. bolt thread is metric-M8x1.25mm.

A 10SI can be had up to 94 amp so I don't see a need to go to a 12SI for where you intend on using it.
Dan

Thanks glasman. That was very helpful.