Alternator pulley diameter, Does size matter? Options

[jack20]

I had my alternator rebuilt by a local auto electric shop. The guy took forever so he delivered it to my house as a courtesy. I immediately noticed that it didn't have the correct pulley with the four notches. It appears to be very close in size but I don't know the diameter of the original.
The day after he delivered it I left on a 3 week trip and told him I would connect with him when I got back. Now I can't reach the guy and am wondering if I can use the one he installed.
Two questions:
1. Could someone kindly measure the diameter and let me know what it is?
2. If the diameter is slightly different will charging be affected?

The belt seems to fit fine in the channel.

Thanks in advance for your help. This is the last step before the engine goes back in.

Jack

[Nozzle]

Check to make sure he didn't simply put the pulley on backwards. Can easily be done and the four slots you mention will be on the backside instead of the front. The same thing happened to me is how I know. If this is the case you'll want to get reinstalled correctly or the belt won't lineup right and you'll be spinning the belt off at regular intervals.

[jack20]

Check to make sure he didn't simply put the pulley on backwards. Can easily be done and the four slots you mention will be on the backside instead of the front. The same thing happened to me is how I know. If this is the case you'll want to get reinstalled correctly or the belt won't lineup right and you'll be spinning the belt off at regular intervals.

I wish it were so. It's the wrong pulley. He has the correct one but he's unreachable.
Thanks for the suggestion.
Jack

[Dave_Darling]

If the diameter is smaller, you will use slightly more engine power to spin the alternator faster. The voltage regulator should keep the battery from getting over-charged.

If the diameter is larger, you might not get as much charging at low RPMs as with the stock-diameter part. But the difference is probably very small, and even if it is noticeable it only matters if you spend most of your time with the engine at idle RPMs. If you're actually driving, the alternator will spin fast enough even with a larger pulley.

BTW, that larger pulley is the sort of thing you see advertised as a "power pulley" for other engines. Because it will take very slightly less power to spin than the smaller-sized ones.

--DD

[jack20]

Thanks very much Dave. Very helpful.
Maybe someone has access to one in the garage and put a tape measure on it.
Jack

[North Coast Jim]

Thanks very much Dave. Very helpful.
Maybe someone has access to one in the garage and put a tape measure on it.
Jack

Just happen to be at the same point as you and I do have the pulley. It measures 3.630" OD on the face that has the 4 slots. The other side is 3.603". The "V" groove root is approx 2.63". I say an estimate because I can't fully get my calipers fully seated into the groove.

[jack20]

Thanks Jim. Mine is so close that I think it will be fine.
I appreciate you taking the time to respond.
Jack