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Old 11-01-2004, 03:45 PM
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Alt pulley not small enough?

Hi guys,

Just installed my 12SI, 100 amp alt into my '52 Hudson. Went in with no problem and started right up after all of my new wiring harness was terminated.

The alt isn't charging at 500 rpm but when I bump my throttle slightly it starts to charge. I'm wondering if I need a smaller pulley on the alt in or order to charge at idle. I'd hate to raise the idle past 500 rpm since the engine really doesn't like a high idle.

Anyone know where I can find very small diameter pulleys?

Thanks folks.

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Old 11-01-2004, 06:04 PM
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alt. pulley ??

What size pulley is on it ?
After you kick up the rpm's does it hold charge ?
Is it a single wire self energized alt ?
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Old 11-01-2004, 06:21 PM
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It shouldn't really be a problem. You normaly don't spend much time idleing, but PAW lists a 2.8" dia single groove aluminum alternator pulley for $30-$35 depending on finish. Measure yours, I think that's smaller that stock. If so, check them out at pawengineparts.com..
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Old 11-01-2004, 09:07 PM
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Does it not charge at idle ever or just when you first start it. A lot of alternators have to be reved up a bit at first to get them started and afterwards, they are OK. Any alternator will only put out a small charging current at low RPM anyway, your original generator likely didn't put out anything at idle.
Unless you like to idle a lot with a big stereo thumping, you may not need to make any changes.
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Old 11-02-2004, 03:49 AM
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Alt/pulley

[size=3]Doc here:

It sounds like the charging system is working just fine...

500 rpm sounds really low for an idle especially if it's an automatic..

Most SBC's run around 650 in drive or reverse,...Slightly lower for manual Transmission.

Hudson may have other ideas.....but 500 Rpm is barely Running...

Larger/Smaller Diameter pulleys might throw some crap into the game too..like under running /over running the water pump speed causing temp problems..so you want to be careful with that.

I'd leave it alone...or if it's Externally regulated, set the regulator to cut in earlier than where it's at now.

Doc
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Old 11-02-2004, 05:54 AM
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ALT Pulley

Thank guys for all the input...here's some more info:

The alt is a typical 3 wire setup wired according to MAD Electrical's wire kit.

The engine RPM at idle is supposed to be 490-510 RPM per the Hudson manual...I have a 262cid straight six.

Once the RPM's have hit, I'd say around 700, the alt starts to charge just fine and continues to charge until RPM's drop.

My only concern is that when I do install my new stereo system I will be needing some serious power....and I cruise a lot and hit a lot of shows where there is a lot of slow driving within parking lots etc.

Doc, you say a smaller pulley could introduce other issues into the system. I thought that the water pump wouldn't even know there was any change...only the alt would since its pulley is smaller and the belt stays the same, you simply take up the little slack that the new pulley produces with the alt swing arm.

My existing pulley diameter is unknown at the moment, I'd have to pull it and measure.

Again, I thank you guys for responding!
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