alternator pulley size 1976 1800

[maluminse]

I bought one from a national dealer and a mom and pop who only does fiat.

Both have pulleys that are about 3 inches smaller than the pulley on my old alternator.

The bolt is a different size so swapping likely will not work. As well AI said that the smaller pulley could cause rpm problems with the alternator.

Suggestions? Source for the correct alternator?

[kaivatony]

That’s a common issue when sourcing aftermarket alternators. Many newer units come with smaller pulleys designed for higher-RPM modern engines, which isn’t ideal for the 1800. A smaller pulley can definitely cause the alternator to over-spin at higher RPMs or not charge properly at idle.

One option is to source a rebuilt OE alternator or look for a rebuild shop that can transfer your original pulley to a compatible unit. Some shops can also re-machine a correct-size pulley to fit the new alternator shaft if needed.

If you’re keeping it stock, you might want to post a WTB in the parts section — someone might have a correct 1976 unit lying around.

[18Fiatsandcounting]

Just curious, what is wrong with your old alternator? While old alternators do fail, the reason that I ask is that it's common for the voltage regulator to fail as well, causing charging problems. Starting in 1977, Fiat switched to an internally regulated alternator on the spiders, but your 1976 should have the external regulator. And the most common issue is simply that the battery connections are really corroded, including the ground strap from the battery negative to ground as well as the large ground strap from the underbody to the transmission bellhousing.

If the old alternator is truly bad, there are three options in my mind:
1) rebuild your old alternator at an automotive electrical shop, if you can.
2) Buy a replacement alternator from the usual vendors like Vicks, Midwest-Bayless, Autoricambi, etc.
3) Find a shop that can swap pulleys for you as Tony suggested above.

-Bryan