Standard Vs. Reverse Rotation Fans
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This subject came up in the context of a swap I did to put a 1987 Mustang 5.0L engine with EFI and a serpentine belt drive into a 1979 F100. By the time it came to installing the engine driven cooling fan, I had a ton of parts laying around from various Ford V8's - some standard "clockwise rotation" fans and some reverse "counterclockwise rotation" fans from engines with serpentine belt drives. You'll see this different in water pumps as well, and it matters just as much for the water pump to get it right as it does with the engine driven cooling fan.

On a conventional V-belt system the water pump and the cooling fan that is attached to it spin in the same direction as the crankshaft. For pretty much all engines (except "reverse rotation" marine engines), this means that the crankshaft, water pump pulley, fan, and water pump impeller all rotate in a clockwise direction when viewed from the front of the engine. On most serpentine belt systems, the belt is run such that the crankshaft spins in a clockwise direction but the water pump pulley, fan, and water pump impeller spin in a counterclockwise direction. A quick visual comparison of the belt arrangement on each setup will show you why. Because the cooling fan and water pump impeller must spin in a certain direction to work correctly, this means that these two components must be matched to the belt system on your engine. Fortunately, on most production American V8 engines (Chevy, Ford, etc.) that were produced with both V-belt and serpentine belt setups, you can simply purchase the right water pump and even the fan clutch (if used) for your application. The engine driven cooling fan, however, is another matter. They generally don't wear out, so that means it's a matter of buying an expensive replacement part (dealer, etc.) or finding one used to match your needs. This page is intended to help people like me who might be scavenging through a pile of used parts (junkyard, eBay, Craigslist, etc.) to find the right cooling fan for your project.

 

Pictures

Here is a picture of a standard (clockwise) rotation Ford fan. This one happens to be an 18" 5 blade fan. Note that you are viewing it from the engine side in this picture. Compare the angle/tilt of the fan blades to the reverse rotation fan in the next picture to see the difference.

FordFans-StandardRotation-18inch-5blade.jpg (2362433 bytes)

Here is a picture of a reverse (counterclockwise) rotation Ford fan. This one happens to be an 18" 5 blade fan. Note that you are viewing it from the engine side in this picture. Compare the angle/tilt of the fan blades to the standard rotation fan in the previous picture to see the difference.

FordFans-ReverseRotation-18inch-5blade.jpg (2209995 bytes)


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Page last updated 01/02/2009 01:51:39 PM