iight i search but i didnt find a post that answered this ? for me. what is the stock output at idle of a 305tbi alt? what would have to be done to upgrade to lets say a 160 or 180amp alt? what are their outputs at idle? im just tired of having 13.5volts when my fans kick on and thats only fans. when im at a stop light add in my brake lights and it goes under 13. forget the a/c and stuff like that, i gotta keep it revved(sometimes to 1.5K or 2K) to keep it aboe 13. its a new alternator that was on there when i got the car(the motor was overhauled)

 

The stock alternator is a 105 amp CS130.

From the description you've given, your alternator doesn't have any problems. They just run like that. As long as they hold 12.8V, you're not discharging the battery.

If you want more output at idle, you can either put a smaller pulley on the alternator, or change out the alternator for a higher capacity unit.

If you want a stronger alt, you want to install a CS144 or a CS130D. It's possible to get an aftermarket CS130 that has been wound for more amps and bolts right in, but I don't recommend it. The CS130's have heat problems, and a higher amperage unit will only be worse. The CS130-D is the same size, but has much improved cooling. The CS144 is much larger alternator, and also cools better than the CS130.

You can see an example of how to fit a 140 amp CS144 unit here. I'm working on a way to fit a CS144 in a serpentine accessory bracket, without having to buy the $40 adapter bracket and hack on the alternator case, but I'm not quite done yet. When I get it done, I'm going to take pics and post it.