[Ramairnacho]

Originally Posted by Formulabruce

This doesn't look like a 12 Si at all. Big tell tale for starters is the plastic fan set up.

Yes im confused I'm my helping my apologies to everyone. I thought his looked like mine an early 10si but then thought mine was a 12 si too. Yes im.confused but mine has a back like this. Originally I thought it was a late 60 s gto alternator. Can an expert tell me what it is. It looked similar in shape to one in ames catalog so I'm confused a little

[racerboy]

RamAirNacho
I believe that is a 10 DN alternator that used an external alternator. That would be correct for a ‘70 GTO, but the Trans Am used an internal regulator.


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[Ramairnacho]

Originally Posted by racerboy

RamAirNacho
I believe that is a 10 DN alternator that used an external alternator. That would be correct for a ‘70 GTO, but the Trans Am used an internal regulator.


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Thanks so I was right or we both wrong lol. It's an original for sure with correct fan and pulley I hope for a 902/993/904. Do if that's true we can say the ames replacement alternator must be a slightly bigger 12 si alternator but bigger steals hp. I know that. I build a driver 72 with a 70 350 out of a Lemans and a 2 barrel,. I used my ac spacers to space out and line up both power steering and alternator ,measured it and installed a only 1 v belt. It worked! I think it added some hp. Ran great with I still had that car, great daily driver I built

[Formulabruce]

Alternators, once "excited", only charge when their is a voltage drop. A good battery and limited load, they dont use much HP.
In New cars there is a tiny Clutch similar to an AC compressor INSIDE the alternator to save that .13% on fuel... LOL
A 10Si is efficient and a 12Si is efficient and probably runs cooler at higher amps.
When it comes to HP, worry more about the fan. A stock Cooling fan and clutch eats the LEAST HP. FACT.