Water pump pulley diameter for 440 AC car

[histoy]

The fan on my '68 Charger 440 AC car has always been noisy.    People stop and turn around to see me coming, even at 30 mph, because it sounds so loud.   The engine always runs cool, even in the hottest weather with the AC on.  I checked the diameter of the water pump pulley, and it measures only 5 inches.  It's smaller than the bottom pulley, which looks strange to me.

I checked my '64 Belvedere that has a 426 engine, and the water pump pulley is 6" diameter and looks close to the size of the bottom pulley.  That fan has never sounded as loud as the one on the Charger.

Could someone tell me the correct diameter for the water pump pulley for my car.  Thanks in advance for your help....Brian

[John_Kunkel]

A/C equipped cars use a smaller pulley on the pump to raise the fan speed for added cooling, the overdrive ratio is 140% of crank speed. At the same time they went to a 6-vane water pump to prevent cavitation at the higher pump speeds.

I believe '68 was the first year they used the overdrive pullies so earlier cars will be close to 1-1 fan drive ratio  (actually about 90%).

[histoy]

Thanks for the info on the smaller pulley size.   Mine appears to be correct, but it sure makes the fan noisy.

[John_Kunkel]

I've never noticed objectionable fan noise with the stock fluid drive and 18" 7-blade fan. There are some fans that have a more aggressive fan blade pitch (cop cars) and they can be pretty noisy.

[histoy]

Unfortunately, mine doesn't have the stock fluid clutch and fan on it yet.   It has a regular 7 blade fan.  I think that the previous owner put in a different radiator, and the only fluid drive clutch that will fit is the short one used on the Hemi cars, which he couldn't find at the time.   I bought a good used one, and I'll eventually find the right fan to use on eBay. 

[John_Kunkel]

Direct drive 7-blade fans are notoriously noisy. Used fluid drives are a mixed bag, I hope it works for you.

There are shorter fluid drives in the aftermarket, one from a certain year Jaguar seems to be the shortest that will fit.