Alternator upgrade

[Billingstitan]

What are you trying to gain by swapping alternators? Yes, a 140, or 145 amp alt, will put out more at say 1000 RPMs plus, but for low RPMs, you need to do an overdrive pulley. This will spin the alternator faster at idle. So the overdrive pulley, is smaller than the OE pulley. I swapped mine on my 105 amp alternator, and it made a world of difference at idle. For me, that's just where I needed more power. Before, with everything on, I was falling down around 9.5 volts at idle. Now I'm at 12.5 at idle.

That’s brilliant. What is a source for an aftermarket pulley, and how do you determine size?

 

[kennythewelder]

That’s brilliant. What is a source for an aftermarket pulley, and how do you determine size?

I used this one, BC is says it fits the cs120 alternator. Fit grate. I was able to use my same belt. I did have to pull off the alternator, and use an impact wrench to remove and replace the pulley. I originally thought that it was a lot smaller than the OE pulley, but it really isn't a huge difference. It's is enough however to spin the alternator faster at idle. It did shift the belt just a tad closer to the radiator, but not enough to worry about. Maybe 1/8 of an inch, or less. Everything still lined up just fine. It is a good swap, if your issue is low voltage at idle. It is about as small of a pulley, as you can install on the cs120 alternator. The bottom pic, is it instead on my truck.

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