Why do some alternators have a 2 belt pulley

[spstan]

and other alternators have a 1 belt pulley? Asking out of curiosity. Paul

 

[FURYGT]

and other alternators have a 1 belt pulley? Asking out of curiosity. Paul

Depends on the belt set up. A/C cars use the second pulley for the compressor.

 

[Snotty]

My AC car uses two belts for the Alternator, Compressor, and Crankshaft.

I don't know the reason for this, but I know from experience, I would rather have two instead of one. If the one breaks the water pump stops turning. Not a good thing.

 

[CBODY67]

A two-pulley alternator can be used "everywhere", a/c and non a/c cars. A single-pulley alternator would have been on non-a/c cars only, which would limit the ultimate number of cars it could work on, plus a lower output item because of that, most probably.

On our '66 Newport Town Sedan factory a/c car, one specific belt for the water pump and related idler pulley. One specific belt for the power steering (the flex mount, so the belts lasted forever). The matched-set belts for the a/c compressor and alternator. In normal use, the OEM and Gates Green Stripe belts had not durability issues, lasting "for ages" before they'd even hint at needing replacement. In the earlier times, the "matched set" belts were sold as pairs, from the same batch number of rubber belting material so their working dynamics were the same. In later years, perhaps quality control improved or manufacturing processes improved enough that they all operated the same?

Enjoy!
CBODY67

 

[413]

1969/70/71 426 hemis used just the forward groove on a 2 belt pulley to run the alternator. A single pulley won't line up.

If you put a 2 belt pulley on a non A/C car it is the rear groove that lines up.