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Author Topic:   Flex-Fans
fran
Journeyman

Posts: 5
From: butler, pa. u.s.a.
Registered: Dec 2000

posted 05-14-2001 09:32 PM     Click Here to See the Profile for fran   Click Here to Email fran     Edit/Delete Message   Reply w/Quote
What is the pro's & cons of flex fans. what is the main purpose of them & are they recomended over the standard fan for a 289 or 302.

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steve'66
Gearhead

Posts: 8796
From: Sonoma,CA,USA
Registered: Mar 2000

posted 05-15-2001 11:28 AM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by fran:
What is the pro's & cons of flex fans. what is the main purpose of them & are they recomended over the standard fan for a 289 or 302.


A flex fan's pitch changes automatically with the speed of its rotation. So, at low speed operation it draws more air through the radiator. It flattens out at high speed creating less drag on the engine. The standard 4 blade (non-air conditioned) fan is fixed and draws more air at higher speeds and uses a lot of h.p. at higher rpms. A clutch fan (a/c cars) uses less h.p. at higher rpm than a flex fan, and draws more air at low speed than a flex fan. But, flex fans are cheaper than a clutch fan.

SteveW

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Tom351
Journeyman

Posts: 93
From: Marietta,GA
Registered: Mar 2001

posted 05-15-2001 11:47 AM     Click Here to See the Profile for Tom351   Click Here to Email Tom351     Edit/Delete Message   Reply w/Quote
And after breaking a blade off of a regular fan, I highly recommend the lighter flex fans for anything that sees high rpm's often. Now I have electric's, but I had a flex fan that cooled well, just make sure it is close to the radiator.

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67 Fastback - Arctic White Pearl paint
351W ,Trick Flow Aluminum Heads, Edelbrock TorkerII, Carter 750 CFM, Comp. Cam 477/510 219/[email protected], Performance Automatic C-4 Trans, 3.55 gears, Front Disc Brakes, 1-1/8" Fr. 3/4" rear sway bars.

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steve'66
Gearhead

Posts: 8796
From: Sonoma,CA,USA
Registered: Mar 2000

posted 05-15-2001 12:11 PM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
As far as horsepower goes, check this out from our archives:

SteveW

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I was reading the May 2000 'Car Craft' and I came across something very interesting. They did a dyno test on a 496 horsepower chubby, {yes, I know -- but we can still get some useful info on this...} and they tested different cooling fans to see what kind of drag each different type has.

Check this out;
Alternator, no fan: 496 hp
Black Magic electric fan: 494 hp
Thermal clutch fan: 487 hp
Nonthermal clutch fan: 485 hp
Heavy duty thermal clutch fan: 476 hp
High performance flex fan: 476 hp
Stock four blade fan: 473 hp
Low profile flex fan: 466 hp
One piece plastic flex fan: 460 hp
OE replacement six blade rigid fan: 449 hp

They found the alternator alone, a 63 amp unit, only sucked 1 horsepower.

I found this very interesting. That's a tremendous horsepower difference between fans!

I use a Ford seven blade flex fan that moves a ton of air, but I'm getting an electric unit!

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SteveLaRiviere/Administrator
'72 Mustang Sprint 351C 4V/FMX and not so puny 4.30 Trac-Lok
'94 F-150 XL 5.8L/E4OD/3.55 Limited Slip
'97 Probe GTS 2.5L DOHC/CD4E


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richard bohm
Gearhead

Posts: 373
From: tucson,az-luray,va
Registered: May 2001

posted 05-17-2001 04:19 AM     Click Here to See the Profile for richard bohm   Click Here to Email richard bohm     Edit/Delete Message   Reply w/Quote
my feeling is the fewer parts in the unit the less there is to go wrong. i have used fan clutches, flex fans, and electric fans. i have almost never had any luck with a fan clutch, they have all(except my F-250) failed
in fairly short order. i currently use a plastic flex fan, it is quieter than a metal one and lighter as well. i will be going to electric fans on my mustang and falcon when i get them on the road.

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PJHMustang
Journeyman

Posts: 35
From: Granada Hills, Ca., USA
Registered: Jan 2001

posted 05-20-2001 09:22 AM     Click Here to See the Profile for PJHMustang   Click Here to Email PJHMustang     Edit/Delete Message   Reply w/Quote
Once years ago I installed a flex fan on my 260 Falcon. With this install I gained a vibration and a overheating problem. I'm not inclined toward flex fans anymore.

Pat

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Rory McNeil
Gearhead

Posts: 1536
From: Surrey, B.C. Canada
Registered: Nov 2000

posted 05-20-2001 01:04 PM     Click Here to See the Profile for Rory McNeil   Click Here to Email Rory McNeil     Edit/Delete Message   Reply w/Quote
I`ve got one of the cheaper Flex A Lite black plastic flex fans on my 302 Fairmont. Works great, not too noisy, temp never goes over 170 degrees (with a 160 thermostat). I find it hard to believe that it sucks 30 HP though... How high were they revving that Chevy anyhow? Clutch fans are OK, but expensive & HEAVY.On my Fairmont, I know if I remove both fan belts, the car picks up 3 tenths in the 1/4. I think the big difference might be due to the large crank pulley.I guess with 2.47 gears, they needed to run the alt.,water pump,& PS pump faster to make everything work properly.Since I have3.55`s in the 8.8, a set of smaller pulleys would work fine,, I believe. Sometime soon, I`ll run the car with the belts on, but remove the fan, & see how much ET it is eating up.

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