Engine Fan Size
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Junior User
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Engine Fan Size
Im in the market to buy a new fan for my engine. How do you decide on what size fan you purchase for your truck? I noticed that broncogravyard has multiple sizes of fan but i dont know how to pick one for my truck. Or even if it matters. I have a 1979 ford f150 400.
thanks dave
thanks dave
Fleet Owner
Joined: Dec 2009
Posts: 20,678
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From: NorCal
If you have fan shroud then it has to fit within the opening - at least 1 inch clear all around because the engine can shift/vibrate and eat into the shroud. With a shroud, a fan should penetrate';/project at least 1/2 inch-into the shroud for efficiency.
Third, watch out for pitch.... some fans have a steep pitch and may interfere with the V-belts. Place your stock fan on a horizontal surface and measure its total depth. Also measure the distance from the fan spacer (while mounted on the hub) to the closest horizontal obstruction (forward and rear-ward) - it's usually a drive belt.
The lighter the fan, the less HP it takes to spin the rotational mass - go aluminum instead of steel. Some even have flexible vanes that flex so there is less aerodynamic drag as engine RPM increases.
If you've ever wondered about variable blade spacing, they were engineered to generate lower noise level.
Third, watch out for pitch.... some fans have a steep pitch and may interfere with the V-belts. Place your stock fan on a horizontal surface and measure its total depth. Also measure the distance from the fan spacer (while mounted on the hub) to the closest horizontal obstruction (forward and rear-ward) - it's usually a drive belt.
The lighter the fan, the less HP it takes to spin the rotational mass - go aluminum instead of steel. Some even have flexible vanes that flex so there is less aerodynamic drag as engine RPM increases.
If you've ever wondered about variable blade spacing, they were engineered to generate lower noise level.
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Alright, well what if my engine didnt come with a fan? It came with electric fans that were ghetto rigged so that when you turn the truck on they go on. Im not the biggest fan of them and since this is my first truck i would like to keep it as basic as possible. So, i was going to switch back to the mechanically driven fan. I dont have a fan to measure anything nor do i have a shroud so would you have any suggestions of what to go with. I think if i remember correctly the shroud all depends on the size of the radiator?
Fleet Owner
Joined: Dec 2009
Posts: 20,678
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From: NorCal
Ah. I now understand your dilemma. As a starting point, I suggest referring to the NPD catalog. I recall it contains a table on what radiator size, fan shroud, and fan diameter your 79 should have.
Electric fans are worth a few HP. Personally, I would probably stick with the electric fans and simply wire them correctly with a thermostatic fan harness kits linked below. :
JEGS Electric Fan Wiring Harness Kits - JEGS
Electric fans are worth a few HP. Personally, I would probably stick with the electric fans and simply wire them correctly with a thermostatic fan harness kits linked below. :
JEGS Electric Fan Wiring Harness Kits - JEGS
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Joined: Sep 2008
Posts: 625
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From: Stafford, VA
Alright, well what if my engine didnt come with a fan? It came with electric fans that were ghetto rigged so that when you turn the truck on they go on. Im not the biggest fan of them and since this is my first truck i would like to keep it as basic as possible. So, i was going to switch back to the mechanically driven fan. I dont have a fan to measure anything nor do i have a shroud so would you have any suggestions of what to go with. I think if i remember correctly the shroud all depends on the size of the radiator?
I just removed mine from my 78 F150 in favor of a taurus 2speed. You can have it for shipping.
Stafford, Va 22556
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