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  •  » FYI Ford, Classic Mustang Tech Discussion
  •  » Fan Clutch vs Flex Fan continue

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    6/03/2020 6:46 AM  #1

    kardad
    I FYI 24-7

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    From: Lexington Ky
    Registered: 12/03/2019
    Posts: 305

    Fan Clutch vs Flex Fan continue

    Sorry for the second post, but I tried everything and couldn’t post photos to an ongoing post.

    This my present setup




    Small amount of leakage


    A 7 blade fan I have (fixed)


    My old electric fan setup

     

    6/03/2020 7:13 AM  #2

    Bullet Bob
    Senior 24-7 FYI Addict

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    From: Montrose, Colorado
    Registered: 4/01/2013
    Posts: 4,887

    Re: Fan Clutch vs Flex Fan continue

    My setup is very similar to yours.  I use a seven blade fan on a thermal clutch with a homebrew shroud on a 20" aluminum radiator.  From the photo it looks like you could add an inch to the fan diameter but other than that...?  How old is the clutch?  They don't last forever.  Mine will handle a lot of idling but will eventually start to warm up.  I run a 194 stat (EFI) and that's where it runs normally.  I drove it Vegas in June a couple of years ago and got stuck in traffic on I-15.  Set for about 30 minutes in 120 degree ambient with the AC on.  Car got up to about 215 but came right back to normal when moving a bit.  I wouldn't get too worked up about 210. I noticed a while back that some of the late model Chevs run there.  I've found that just a bit of fast idle will usually bring mine back to normal if I have to sit for a while.

    BB1

    "you get what you pay for, good work isn't cheap, and there are NO free lunches...PERIOD!"
     

    6/03/2020 7:58 AM  #3

    TKOPerformance
    Hyper FYIFORD ADDICT

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    From: Newark, DE
    Registered: 12/15/2014
    Posts: 7,510

    Re: Fan Clutch vs Flex Fan continue

    BB, I'd be inclined to agree if the car consistently ran at 210.  The issue is that he's seeing higher than normal temps when the ambient temp isn't high.  I share his concern, and I know where he thinks he might be headed (230 in 95 degree heat and worry about boilover). 

    Modern cars all run over 200.  My '86 IROC didn't even switch the fans on until it hit 220.  That was too much, and I had to correct that once I started modifying the car, but that was also a first gen single electric fan car.  I've never much looked at the later vehicles in my stable, because I've yet to have a problem with any of them cooling system wise beyond the typical need to replace the plastic/aluminum radiator after 10 years or so due to leaking. 

     

    6/03/2020 9:19 AM  #4

    red351
    I FYI 24-7

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    From: Carlisle, PA
    Registered: 5/31/2018
    Posts: 445

    Re: Fan Clutch vs Flex Fan continue

    May need to step up to heavy duty clutch with larger diameter fan and more so with 7 blades. Aftermarket standard duty clutches are very weak. A severe duty will move a lot air, but sounds like an aircraft on takeoff till it loosen up a few miles down the road.

     

    6/03/2020 10:50 AM  #5

    Bullet Bob
    Senior 24-7 FYI Addict

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    From: Montrose, Colorado
    Registered: 4/01/2013
    Posts: 4,887

    Re: Fan Clutch vs Flex Fan continue

    Original Post:

    "Everyone's favorite topic, over heating.

    Well its not really over heating yet. My 68 coupe with the 24" radiator and factory shroud and clutch fan with 180 degree stat. Typically it stays between 180-190 and if out on the road, even driving spiritedly it will stay right at 180 on a 80 degree day.

    Well today it is beautiful out so I decided to drive the car to work, and while setting in a drive thru for some lunch (sat way too long) the temp started creeping up. By the time I got out of the drive thru it was between 205-210. As soon as I pulled out and headed down the road the temp began to fall.

    So I know it is an air flow issue not cooling capacity. I guess I am questioning if the fan clutch is good first? If I start the car cold and let it idle and build heat, the motor will heat up to about 190ish and the stat will open and the temp will drop to 180. I never really hear or fill a difference in airflow as the air heats up across the radiator.

    I assume once the system heats up, the fan clutch should be harder to spin when I shut it down.

    What are the opinions of those running a mechanical system, FAN CLUTCH vs FLEX FAN.

    On a final note, I have an open lower valance similar to a Shelby."

    I guess I misread this.  I thought it said that it only heated when he sat idling for a long time but went right back to 180 when he drove away.

    BB1

    Last edited by Bullet Bob (6/03/2020 10:51 AM)

    "you get what you pay for, good work isn't cheap, and there are NO free lunches...PERIOD!"
     

    6/03/2020 7:51 PM  #6

    kardad
    I FYI 24-7

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    From: Lexington Ky
    Registered: 12/03/2019
    Posts: 305

    Re: Fan Clutch vs Flex Fan continue

    Update,

    I installed the 17” fixed blade fan without a fan clutch. I ran the motor up to temp and let it idle for 20
    Minutes. Outside temp was 88 degrees. Running around the neighborhood it never got over 185, idling in the drive it got to 197.

    I then ran the idle up to 1600 rpm for 2 minutes and it instantly dropped to 190. So I feel it is definitely a airflow issue.

    A couple things, first going to the fixed fan I expected it to be loud and feel a power drop, but there was no noticeable power drop or increase in sound. I looked at the pitch on the blades and I believe they are too flat on both fans I have. I compared both of them to an old one from a 96 F150 351, it had a 7 blade 18” fan.

    The two Mustang fans have a blade pitch of 30 degrees, and the F150 fan blade pitch are 40 degrees. I feel like the pitch is too flat and that is why it doesn’t make any noise while winding up.

    I think the answer is a 18” 6-7 blade fan with a steeper pitch on the blades. Unfortunately the F150 fan is a reverse rotation fan.

    It was surprising how much difference a few hundred RPMs made in airflow. At 800 idle RPM the fan moves little air, but it increases 3-4 times just off idle 200-300 RPM.

       •Thread Starter
     

     

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