Difference between clutch fans
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Joined: Mar 2002
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From: Colstrip, MT
Difference between clutch fans
Can somebody tell me what the difference is between a heavy duty clutch fan and a severe duty clutch fan and what are the applications for each fan?
This is for a '78 F-150 4WD 400 w/ factory AC.
This is for a '78 F-150 4WD 400 w/ factory AC.
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Joined: Nov 2004
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From: Asheville, NC
Is this aftermarket?
I know that Ford used a different fan for each engine family, and also a different fan between A/C, and non A/C.
The fan clutch? I'd replace what you have with a factory-style. Also, use a shroud. The truck will thank you.
I know that Ford used a different fan for each engine family, and also a different fan between A/C, and non A/C.
The fan clutch? I'd replace what you have with a factory-style. Also, use a shroud. The truck will thank you.
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Joined: Mar 2002
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From: Colstrip, MT
Yes, it is aftermarket. I have a choice of two options: heavy duty or severe duty. I do have a shroud in place. I have replaced every other part of the cooling system, as a restoration.
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Joined: Jun 2003
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From: Houston/Hope BC
Without seeing what you are buying, I can tell you a little about the two clutches I have seen over the years. The smaller one (which would be standard duty to me) has an exposed spring on the front, which I presume operates the internal coupling in some manner. The larger one (which is HD to me) looks heavy duty, it is larger and includes some fins that I presume aid in the response time of the viscous coupling. The smaller seems to appear mostly on passenger vehicles and 302 equipped P/U's. The bigger one sure seems to do a lot better job for me. I upgraded many years ago on my 400 and I think the clutch was over $80.00 new at NAPA.
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From: Colstrip, MT
Thank You. The spring on the end of the clutch is for a thermally operated fan. My search on the web told me that the standard duty clutch fan turns at about 50% of the engine rpm, heavy duty turns 70 - 80% of the engine rpm, and severe duty turns at about 90% of engine rpm. They also make a non-thermal application without the spring on the end. I went with the severe duty. With 2 1/2 inches of pitch on the fan blades, I was told that the fan would produce enough airflow for the severe duty to work properly, with a small sacrifice in gas mileage(12 mpg to 11 mpg).
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