Alternator Pulley wrong size

[Praxiss454]

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):


And here's what the pulley looks like on a new one from the store:


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.

[Rickysnickers]

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.

[Praxiss454]

Originally Posted by Rickysnickers

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.

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.

[jtrichard]

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?

[jtrichard]

Ricky he has A L6

[Praxiss454]

Originally Posted by jtrichard

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

Wow, look at those prices.

DID you get the lower bracket corrected?

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

[jdl71]

Originally Posted by Rickysnickers

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.

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

[jdl71]

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

[TJ's Chevy]

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.

[Warrens69GMC]

can you use a double groove pulley?

[jdl71]

Originally Posted by TJ's Chevy

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.

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

[Praxiss454]

Originally Posted by jdl71

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

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.

[WOLFMANmike]

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 ?

[Praxiss454]

Originally Posted by WOLFMANmike

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 ?

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.

[Rickysnickers]

Originally Posted by jtrichard

Ricky he has A L6

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

[wahl4m]

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 !

[jdl71]

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.

[DPowers]

The one off this motor help you at all?

[jdl71]

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.

[jdl71]

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

[DPowers]

230/250 Casting Number is:3921968

[Praxiss454]

Originally Posted by DPowers

230/250 Casting Number is:3921968

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.

[DPowers]

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.

[Praxiss454]

Originally Posted by DPowers

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.

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.

[jtrichard]

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