water pump pulleys, bigblock, non-AC - 3 different sizes???

fury fan

Senior Member
Mar 30, 2013
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I have a question about non-AC bigblock water pump pulleys.
To my knowledge, there are at least 5 different belt-drive setups for 65-78 bigblocks, even more if you include Industrial engines, Leece-Neville alternators, etc.
Below-left is the 'standard' 6-13/16" dia pulley that is available from several reproduction outlets, and is noted for 65-74 bigblocks without air. The one on the right is the smaller diameter for the Hemi (is approx 5" dia?).

Reason for my question -
I took all the pulleys off my 3 cars and sent out for powdercoating about 6 mos ago.
1 of the pulleys is just barely smaller than the big one, at 6-7/16". Looks just like the left pulley but slightly smaller dia, cannot notice unless they are side-by-side.
At the time, I wrote some notes of which car was wearing which pulley - and now can't find my note. :BangHead::BangHead:
It's not critical (I think the car that typically runs the hottest will get the smaller pulley) but I'm simply curious if anyone knows what this pulley is from, and why the factory deemed to make one a mere 3/8" smaller.
(all of my crank pulleys are standard 2-belt variety and all same dia)

Anyone know???



Old Man with a Hat
Mar 27, 2011
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As you are dealing with a non-a/c set-up, it might not make much difference. WHERE it will make a difference is with the belt that fits that combination. Which means that getting into a belt catalog, paying attention to the belt length and width, might answer your question?

The a/c water pump is allegedly the trick pump for hp use, with its 6 blade impeller, but the water pump pulley is smaller, to run it faster, on the a/c car. So using the larger non-a/c pulley with the 6 blade impeller results in lower horsepower drag on the motor.

Just some thoughts,