Pulley Diameters

mbaird said
According to this chart the factory only overdrove the pulleys for a/c & C.A.P cars.
Is that to move water faster or spin the compressor faster ? Remember these engine idled at pretty low rpms stock.

Also notice that trailer tow pkgs underdrove the pump.....

It would be interesting to see what happens if you were to try underdriving the pulleys since you already have a baseline.

I agree that the pusher fans are not doing you any favors especially when off.

Other variables such as....is the car properly tuned ? Was the cam degreed ? Is the block bored to the max ?
May be the issue...

RustyRatRod said
I bet it's to spin everything faster. Remember, the stock Mopar charging system is sub-par at idle. Which is ok if everything is stock. But start adding additional loads and it needs help. So the alternator needed to speed up, too. See the thing is, adding the load of the A/C slows the entire engine down at idle. Yes, there were idle solenoids, but they weren't effective 100%, so the pulleys made up some of the difference.

I believe it was mostly to spin the fan faster. The AC condenser blocks airflow though the radiator, so overdriving the fan would move more air to help compensate.

The down sizing on the water pump that was done on the cars with overdriven pulleys kind of indicates that they didn’t want a big increase in water movement. The standard pump with the overdriven pulley might move a little more water than the HV pump with the slightly underdriven pulley, but it would be close.