Where can I find pulleys?

[ArkShark]

My alternator in my 77 vette has a pulley that is too big in diameter. (~2")

Because of this, I have to rev the engine up to around 1500 before the GEN light will go off, but since my idle is at a nice 550, the alternator kicks off, and the GEN light comes on. This is a problem when I'm driving up to a stop light.
I hit the brakes and the radio kicks off, all the lights dim... etc...

I had the alternator tested, and it is fine. The battery may be low in voltage (less than 12.5), but its still works.

What I need to do is have the alt spin faster so it will work at lower rpms.

However, I haven't found any supplier for small replacement pulleys.
Any idea where I can find any? Or any ideas on how to fix this problem?

Thanks.

 

[Bob Chadwick]

Actually I think your problem might be the other way around. Under drive (smaller) pulleys are supposed to increase horsepower by spinning the accessories slower and taking less power from the engine. They are a common swap.

The vendors should haver the stock pulleys.

 

[Jack]

My alternator in my 77 vette has a pulley that is too big in diameter. (~2")

Because of this, I have to rev the engine up to around 1500 before the GEN light will go off, but since my idle is at a nice 550, the alternator kicks off, and the GEN light comes on. This is a problem when I'm driving up to a stop light.
I hit the brakes and the radio kicks off, all the lights dim... etc...

I had the alternator tested, and it is fine. The battery may be low in voltage (less than 12.5), but its still works.

What I need to do is have the alt spin faster so it will work at lower rpms.

However, I haven't found any supplier for small replacement pulleys.
Any idea where I can find any? Or any ideas on how to fix this problem?

Thanks.

A smaller pulley at ALT will spin ALT faster ... or a larger CRANK pulley will do the same. All performance stuff I've seen is the reverse ... slowing accessories down.

A 2" ALT pulley seems about right for stock ... so your problem shouldn't be due to pulley (unless you have an undersize crank pulley). Also, V-belt pulley smaller than 2" is probably gonna overstress the belt as it tries to bend around such a small radius. I do not believe the problem is your ALT pulley.

I dunno what it is, but I'd look for something other than pulley. Maybe get a different test & opinion of alternator's condition?

-edit- Many of the hopped-up aftermarket alternators (i.e. "one-wire" / high-amperage) tend to cut-in real late and at higher rpm ... dunno about yours.
JACK:gap

 

[Bob Chadwick]

Jack,

Now that you post this I think back to my 10 speed. Smaller gears on the wheel equalled harder work and more wheel revolutions for the same number of revolutions on the front pedals. It was the reverse for the pedal end gears with larger gears up front making harder work and more revolutions of the wheel.

How do these underdrive pulleys work? I was under the impression that they are smaller but that wouldn't make sense because the pulley would actually require harder effort. Is the accesory pulley actually larger? Or is it a smaller pulley on the crankshaft? Or both?

ArkShark, sorry for the misleading information.

 

[C3forME]

Are you sure that you have the correct alternator in your car? Most older Vettes have had the alternator replaced at one time or another, and it is possible that it may have had the incorrect alternator put back into it. My 77 had the incorrect one in it when I purchased it. My car was originally an A/C car and came from the factory with a 65 Amp alternator, however someone replace at one point with a 43 Amp one for a non-A/C car. I replaced it with a brand new chrome 100 Amp unit and have absolutely no problem with dimming lights, slow turn signals, slow wipers, or anything else when there is load on the system.

 

[Jack]

Jack,Is the accesory pulley actually larger? Or is it a smaller pulley on the crankshaft? Or both?

Either ... in some kits it's both.

Our circle track car requires greatly reduced wp & psp speeds … only for race … not for street at all. I use an aluminum short wp but with wp-block spacers to align w/ long style crank pulley.
http://moroso.com/catalog/categorydisplay.asp?catcode=31100http://moroso.com/catalog/categorydisplay.asp?catcode=31003
We’re running 4” P/N 64111 on crank and 7” P/N 64902 on water pump. We drive the PS pump off the second crank groove. We don't have alternator ... but may go to one. Regardless, may go to serpentine drive. But it won't be boy racer stuff like March ... probably CV Racing, KRC or Sweet.
JACK:gap

 

[ArkShark]

It is a replacement (chrome, 135 amp) alternator.
I purchased it from Alterstart. They said it was for a 77 corvette.

It spins to slow. (at idle)

The pulley I got with the new alternator is actually smaller than stock, but obviously not small enough!

If I rev the engine to about 1200, the GEN light will go off, but when the RPMs fall below 700, then the light comes on. (and everything electrical dims).

Annoying little problem.

 

[lone73]

Sounds like you have something pulling too much juice with the key on. I'd try popping out fuses until the gen light goes out when idling to isolate the faulty circuit.
good luck
.
.
.

 

[KevinZ]

The replacement alternator is actually for racing, if you put a stock one back on you will be fine. I had the same trouble 'till I went back to stock. Seems the chrome ones are for racing and street performance needs the rev to get them going and they dont need low speed charging.

 

[MrGibbly]

This is interesting to me ArkShark. I have a similar problem with my '78 L48. My alternator isn't one of the fancy high-output chrome models. It's just what Autozone's computer said is right for my car. The Gen light comes on solid any time I am below about 1,000 rpm. I don't have the dimming of the lights, etc. however... As I build rpm the Gen light gets dimmer and eventually flickers on and off but never stays out. The alternator has tested fine at a couple of different parts stores. Odd...

 

[KevinZ]

This is interesting to me ArkShark. I have a similar problem with my '78 L48. My alternator isn't one of the fancy high-output chrome models. It's just what Autozone's computer said is right for my car. The Gen light comes on solid any time I am below about 1,000 rpm. I don't have the dimming of the lights, etc. however... As I build rpm the Gen light gets dimmer and eventually flickers on and off but never stays out. The alternator has tested fine at a couple of different parts stores. Odd...

They test the alternators at aproxomatly 2,000 rpm. Try a new one and I feel you will see a difference.