The Stovebolt Site Forums The Shop Area Engine Shop Belt Sizes for Water Pump/Alternator

Putting the water pump adapter bracket on a '60 235. Have to change the balancer and will be going with an alternator. So I need to decide on pulley width. I want to go with 5/8" if only because the water pumps with this side pulley are cheaper. But what about alternators? Are the 10si alternators all the same pulley width and, if so, what is that width?

The 5/8" belt generator pulley will fit fine on an alternator if you put a washer on the shaft first to space it out from the body.
You can buy a 5/8" alt pulley (sample) .

OK but do GM alts come with a stock pulley size? No use saving $20 on a water pump if I have to spend it on a different pulley for the alternator.

They come with the smaller pulley.

Don, what size is the smaller pulley? 3/8?

yes

Awesome.

Was trying to figure out today why the 3/8" pulley water pump costs more (and much more in some instances) than the 5/8". It's because the 3/8" was on so many fewer engines for fewer production years.

So a debate (in my mind) lingers on. Go with the 216, 5/8", balancer, 5/8" water pump and change the pulley on any altnerator I'll ever need and use, or go 3/8" with everything but spend more on water pumps...

Flip a coin, a case can be made to go either way.