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Flex fans

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by MR.GADGET, Jan 10, 2002.

  1. MR.GADGET

    MR.GADGET Registered Member

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    Anyone use a flex fan on a 350EFI with any luck? Don't know if they will work well at slow speed or when its real hot like running on a beach 90+Deg outside.

    IF IT'S NOT AS BIG AS YOU ARE DRIVE OVER IT!!!!!!!!!!
     
  2. TorkDSR

    TorkDSR 1/2 ton status

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    just a question, but isnt that what the truck came stock with, or is that the wrong word for the flexy metal fan that my truck has on it ??

    beligerence doesn't justify intelligence.
    <font color=blue>wheelers hate posers.</font color=blue>
    <font color=red>79k15/400/700r4/205/38.5</font color=red>
     
  3. holyjohnson

    holyjohnson Registered Member

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    im using a 19" flex fan on my 350 now its not an EFI motor.only overheated once sitting in traffic pulling a boat in august.im still considering electric fans in front for the bigger tranny and oil coolers though.
    flex-fan is an aftermarket brand name for a fan that gets wider at higher RPMs i dont think any manufacturers put them on stock,most have clutch type fans.
    goodluck

    "well,are you gonna pull them pistols,or whistle dixie!?"
     
  4. ChevyCaGal

    ChevyCaGal 3/4 ton status

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    Flex fans are sharp as hail... they flatten out when they get going, are loud and not good for the water either if you wheel in it... I was going to get one but I opted not too because it wasn't a good choice for me....

    &lt;&gt;&lt;<a target="_blank" href=http://www.chevycagal.homestead.com/steph.html>Steph's Webpage</a>&gt;&lt;&gt;
    Suck Fumes Ford Boy
    I'm in shape.... round is a shape......
     
  5. Bubba Ray Boudreaux

    Bubba Ray Boudreaux 1 ton status

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    I've got one on my '87. Doesn't improve anything except the caution factor when it has to be taken off. I've bled like a stuck pig after coming into contact with it. Go electric.

    Bubba Ray Boudreaux,
    Official Colorado K5.com Fantasy Football Choke Artist!<a target="_blank" href=http://community.webshots.com/user/mdntrdr1>http://community.webshots.com/user/mdntrdr1</a>
     
  6. xnoahx

    xnoahx 1/2 ton status

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    ive got one on mine, makes a lot of noise and feels like it moves more air. power wise Im not sure if it will make a difference over a clutch fan.

    My 73 K5 <a target="_blank" href=http://www.geocities.com/xk5blazerx/73k5.htm>http://www.geocities.com/xk5blazerx/73k5.htm</a> 350/TH350/NP203, Q-jet, Edelbrock intake, Vortec heads, 4" lift, and 36" TSL's
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    Depends who you talk to : )

    If I was talking flex fan, I'd be talking about a fan that doesn't use a clutch, and that has blades that are "flexible" that are designed to "flatten out" at higher RPM's. (aftermarket basically)

    Stock is either a hard metal fan without a clutch (which is relatively uncommon after the mid 70's or so apparently) or a hard metal fan, with a clutch. The clutch "locks" up at a certain temp, around 210-220 apparently, and when the engine temp is below that, it "unlocks" to prevent drag on the engine, and since it is no longer trying to move air, its basically just sitting there. The clutch also "stalls" (stock ones, cheap aftermarket replacements don't have a temp lockup feature) as the RPM's increase, again, because the faster the vehicle moves, the less a fan helps.

    Inherent problem with a flex fan (aftermarket and even a stock non clutch) is that the engine is FORCED to turn the fan, regardless if the engine needs the cooling or not. Aftermarket flex fans "flatten out" to reduce this drag, but unfortunately, a big flat "plate" spinning just in front of the radiator blocks the incoming air, meaning the radiator can NOT work as efficiently. So at higher vehicle speeds, you have a big disk reducing the amount of air over the radiator.

    inherent problems with the stock clutch fan are that they take a bit of power to turn, and that at idle, they are tied to engine speed, when higher airflow can be used.

    This is why electric fans are about the best thing you can run. They can be shut off by engine temp, activated by engine temp, setup for manual on/off, very low "power" loss from running them, (alternator drag only) and probably most important, they are not tied to engine RPM's, so at idle or 2500RPM, the fan speed is constant. Not true with stock or aftermarket clutch/flex fans

    I like the picture of the blade of a flex fan sticking through the truck hood. Should have saved that one, can't find it now. : (

    Dorian
    My tech/links page: &lt;a target="_blank" href=http://www.dorianyeager.com/index2.html&gt;www.dorianyeager.com/index2.html&lt;/a&gt;
    Why insist on counting when the ring gear has the tooth counts stamped in?<P ID="edit"><FONT class="small">Edited by dyeager535 on 01/11/02 06:06 PM.</FONT></P>
     
  8. 1bigk10

    1bigk10 1/2 ton status

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    After having a blade break off and fly 3 inches in front of my face and land 40 feet from my rig I definitly would not recomend a flex fan they ate just plain unreliable and dangerous. Just get a heavyduty fan clutch and your cooling system will benifit from it dont make a comprimise with safety to get more air flow when a good steel fan actualy does a better job. Tha flex fan actualy works like this- at low engine speeds the fan draws more air at higher engine RPM's the fan flattens out and draws less air and uses the air bein forced into the radiator by the moving vehicle to cool the radiator and allowing less drag on the engine supposedly giving better feul economy probably does bt that up to you on what you use.[​IMG]

    1982 K10 Silverado. [​IMG] 327 SHPE powerplant SM465/205,15"custom lift 38.5"TSL/SWAMPERS 12boltrearD44 front,3.73 gears.
     

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