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Technical Flathead pulley and belt help

Discussion in 'The Hokey Ass Message Board' started by Rob28, Jul 24, 2019.

  1. Rob28
    Joined: Oct 25, 2014
    Posts: 103

    Rob28
    Member
    from Calgary AB

    Hello all
    Just staring to figure out my fan belts with the pulley and fan set up I have. What size dose the flathead usually use for fan belts my power gen alternator and water pump use 5/8 but a 5/8 belt almost bottoms out in the crank shaft pulley [​IMG]
    [​IMG]

    A 3/4” belt seems to fit best in the crank and fan but rides too high on the water pumps/ alt
    [​IMG]
    I thought that the flatheads either used a 3/8 or a 5/8 belt. I’m not sure of the origins of the crank pulley( on pice cast) or the fan as the person I purchased the engine from included them.
    [​IMG][​IMG]
    What am I missing was there a 3/4” fan assembly for these engines or do the 5/8 belts just run that low in the grove
    Thanks


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  2. Aaron D.
    Joined: Oct 27, 2015
    Posts: 818

    Aaron D.
    Member

    I just run a 5/8" belt on mine. It does fine.
     
  3. BJR
    Joined: Mar 11, 2005
    Posts: 6,507

    BJR
    Member

    Get a look at the bottom of the belt as it goes over the pulley. If the bottom of the belt is not touching the bottom of the "V" of the pulley, you are OK. The belt is not suppose to bottom out on the pulley.
     
  4. alchemy
    Joined: Sep 27, 2002
    Posts: 15,851

    alchemy
    Member

    You've probably got 49 Merc or truck crank pulley and fan pulley, and regular car pumps. The Merc and truck used wide belts, the cars used the narrower.
     
    clem and walter like this.

  5. Rob28
    Joined: Oct 25, 2014
    Posts: 103

    Rob28
    Member
    from Calgary AB

    Thanks everyone
    The 5/8 belt has about 1/16-1/8” before it bottoms. I suspect you are right about the Merc/ truck pulley and fan. Think I might use the larger belt on the fan so it looks corer and try running the 5/8 belt for the pumps and Alternator. Maybe keep a eye out for a standard pulley and fan
    Thanks Rob


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  6. clem
    Joined: Dec 20, 2006
    Posts: 2,990

    clem
    Member

    3rd pic down, is close to how belt should sit on pulley.
    Top two pics don’t look to be correct.
     
    Last edited: Jul 27, 2019
  7. You have a truck fan and I think a Merc lower pulley. The trucks used an 11/16" wide belt for the pumps and generator.....pretty hard to find now, the 5/8" should work there. I use a 3/4' belt for the truck fan.
     
  8. Rob28
    Joined: Oct 25, 2014
    Posts: 103

    Rob28
    Member
    from Calgary AB

    I figured I should update this with my final resolution.
    Lesson 1 don’t trust anyone at Napa to order belts by Size

    Turns out my crank pulley is the one with two different sizes 5/8 for the water pumps and hen and 3/4 for the fan belt never noticed this until I had the balancer off the other day

    Turns out I needed a 37”x3/4 fan belt and a 57x 5/8 belt for the water pumps and my off set generator
    IMG_1470.JPG
     
    RMR&C likes this.

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