Alternator Pulley wrong size
 

Hi folks,

Trying to figure out why my belt isn't straight, and I realized the pulleys on new alternators are the wrong size for our trucks.

Here is an OEM style alternator pulley (photo credit to jdl71):
https://lh3.googleusercontent.com/Fy...t=w400-h973-no

And here's what the pulley looks like on a new one from the store:
https://lh3.googleusercontent.com/8y...O=w400-h751-no

As you can see, on the OEM style pulley, the belt groove is about 1/2" farther forward. When I install a new alternator, my belt is misaligned. So what gives? I do not have an OEM pulley and have not been able to find one anywhere. Any tips on how you handled this problem are much appreciated.

Re: Alternator Pulley wrong size
 

What kind of water pump do you have, long or short? The original is sized for that pump, or at least it's my opinion FWIW.

Re: Alternator Pulley wrong size
 

I don't know what pump I have, but I do know the fan pulley and crankshaft pulley are both in line with each other, and when I try to install a replacement alternator, it is about 1/2" too far backwards and the belt won't line up.

Hoping someone knows a part number for the OEM alternator pulley, or has found a repop or aftermarket pulley that is the same dimensions.

Re: Alternator Pulley wrong size
 

Look at the pics of the restored one then you may want the reproduction one these look like what you have with you old wore out pulley

http://www.ebay.com/itm/Original-Res...ZW9Dqd&vxp=mtr

http://www.ebay.com/itm/1963-1965-19...-/262392203559

You may be-able to use one of these and only use the outer groove

http://www.ebay.com/itm/Chevy-GM-Chr...NULEug&vxp=mtr

DID you get the lower bracket corrected?

Re: Alternator Pulley wrong size
 

Ricky he has A L6

Re: Alternator Pulley wrong size
 

Wow, look at those prices.

Yes, turns out the reason for my janky bracket was to account for this weird pulley offset difference.

Re: Alternator Pulley wrong size
 

I didn't know there were different water pump lengths for the L6, though that was mainly a small block thing.

Re: Alternator Pulley wrong size
 

I'm wondering if maybe you could just redrill one of those brackets. Since you have two now, you can experiment. :)

Re: Alternator Pulley wrong size
 

The inline 6's used a special alternator pulley that is Not reproduced. Best thing to do would be to swap the old one onto the new alternator. I did this for my 292 and things were back to normal. With some wire brushing and paint I'll be good to go.

Edit: Funny thing is the design of your pulley is different from mine. I may have one if you need it. Whoops....that was JD's alternator.

Re: Alternator Pulley wrong size
 

can you use a double groove pulley?

Re: Alternator Pulley wrong size
 

Learn something new everyday. I had no idea that was a L6 only pulley.

Re: Alternator Pulley wrong size
 

TJ, if you do have a pulley like that let me know. I have some washers in place as spacers but it's still not lined up perfectly and not much of the nut is on threads.

Re: Alternator Pulley wrong size
 

here is a question for ya maybe its stupid or over thinking it but what about cutting you some metal tubing the half inch needed and putting it behind both mounting spots on the Alternator in effect pushing the alt forward the bit you need ?

Re: Alternator Pulley wrong size
 

I thought about something like that but the alternator mounting hole is solid so I don't see how it would work without modifying the alternator.

Re: Alternator Pulley wrong size
 

Ohave, OK. I didn't realize that. Sorry, as you were.

Re: Alternator Pulley wrong size
 

you just need the right pulley! im sure the right one is hard to find maybe in your area! if you old one is not available/ post a wanted ad here !! or ck in your town for a alternater /starter shop ! im sure they might have one in there core pile !

Re: Alternator Pulley wrong size
 

That is a good idea about the starter/alternator rebuilders shop. Also might try a self service junkyard if there is one nearby, you could probably pick up a whole alternator with pulley attached for about the same as buying a pulley and paying shipping.

Re: Alternator Pulley wrong size
 

The one off this motor help you at all?

Re: Alternator Pulley wrong size
 

He needs one like in the very first pic, that has about a 1/2 spacer between the alternator fan and the pulley itself. It moves the belt forward about 1/2 or so.

Re: Alternator Pulley wrong size
 

That is a 6 cylinder though isnt it? Is that a 250?

Re: Alternator Pulley wrong size
 

230/250 Casting Number is:3921968

Re: Alternator Pulley wrong size
 

DPowers, that pulley doesn't look deep enough. Sounds like the consensus is that people reuse their originals and they aren't made anymore but I like the idea to call a rebuild shop. We don't have a close pick n pull place, the closest one is across a toll bridge.

I didn't intend for this thread to be a WTB thread. I'll check the shop as suggested or post in the classifieds.

Re: Alternator Pulley wrong size
 

Didn't think it was a WTB thread. If it will work for you, you can have it.
If scrap was up, that motor would already be gone.

Re: Alternator Pulley wrong size
 

I appreciate the offer! Do you have a picture of the bottom of that engine? I'm curious how the alternator is mounted, and if it uses the original bracket. I don't see how things could be in line on that engine w/ that pulley and the original alternator bracket.

Re: Alternator Pulley wrong size
 

DPOWERS if you want to turn that engine into a pay it forward offer i need the frame half of the motor mounts from both sides and there is a guy that needs the engine half of both sides and im sure that Praxiss454 could use both upper and lower alt. brackets looks like that would solve his dilemma rather than see it all junked