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Discussion Starter · #1 ·
I bought one of thoes chrome 100 amp high-output alternators from a while back, and it seems the belt rides high on the pully, sticks up over the pully about 1/4 inch or more. On my old alt., the pully was much wider in diameter and the belt rode down in the pully deeper. I also noticed that I only get 12.85 volts at the battery when the car is idleing, but it goes to 14.00V when the engine is revved high. I heard that I should be getting at least 13.50-14.50 volts with the engine idleing. My questions are:

1. Would the smaller pully and smaller groove on the new alt. be sacraficing me RPM's causing the drop volts at idle?

2. What can I do to increase the RPM's of the alt. pully at idle for more volts.

I replaced the voltage regulator and alt. wiring harness at the same time as the new alt.

The reason I am concerned about this is because I will soon be adding an electric fan to this car, and they said the fan blows more CFM's with the more volts you get to it, espessially at idle would be helpfull. Any help or recommendations is appreciated! Thanks gang.
 

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I had a similar pulley on my Powermaster alternator (re-packaged Delco 12Si). I removed it because:
1) belt rode too high on the pulley, and was causing the premature destruction of the belt
2) Damn pully could not be held in place and would eventually start squealing.

I re-installed the stock pulley from my old Ford alternator. no more problems.

Regarding your comments on the alternator pulley size, here are the answers:
1) No. Actually a smaller pulley will increase the alternator speed. See #2 below.
2) Smaller alternator pulleys will cause the alternator to spin faster. Think about it.The alternator shaft wil turn faster if you get the belt closer to the center of the alternator. Larger pulley slows the alternator down. So, to increase the alternator speed, install a smaller diameter pulley on the alternator!
 

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Discussion Starter · #3 ·
Hey thanks steve, ya, that makes sense, the pully is very small on that new alt. I think i'll throw the electric fan on there soon and if theres any problems with running it, I was looking at thoes 3G alt. units. Thoes should do the trick. Thanks again! james.
 

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As Steve said, the closer the belt to the center, the faster it'll spin. Some other things you must remember are that from the factory, the crank and alt pulley are mached to the gearing of the car to keep the rotor speed in check and not to explode it from too high rpm. Also, alternators have a specific rpm band that they operate in, they're not a continious and endless source of power that most people think they are.

Keep in mind the gauge of wire for the alt. from the factorty it's barely sufficient for the stock alt. with a 100 amp unit, you'll cook it! Not to mention the voltage drop across it from being a small gauge.

I think most people should read up on basic electricity before making wholesale changes to their charging system. As an electrician, I'm keeping my stock alt. with my stock wiring!
 

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Discussion Starter · #5 ·
Thanks again for all thoes who replyed. And also to Tom for pointing out the fire hazard for the wiring to the alt. I got to thinking about it, and also checked out the wiring, it looks like its only a 10 ga. wire that feeds off of the alt. Much too small for any heavy duty use as I will soon have, ie, electric fan, a/c, and 240 watt stereo. I went to Autozone and picked up a two foot 4 ga. battery cable and used that for the main feed off of the alt. And then simply attached the original alt. wire to the starter solinoid. I feel much better about that setup. Thanks again for all your help gang! James.
 
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