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Hot Rods 1/2 V-belt on 5/8 pulley?

Discussion in 'The Hokey Ass Message Board' started by Johnny Nitro, May 25, 2019.

  1. Johnny Nitro
    Joined: Sep 28, 2005
    Posts: 60

    Johnny Nitro
    from Chicago

    Hey, all

    Couldn’t find an answer to this using search function:

    Is it ok to use a 1/2 wide V-belt on a pulley designed for a 5/8 wide belt, at least for a short while?

  2. theboss20
    Joined: Dec 30, 2018
    Posts: 230


    How long is a while? If it’s an emergency...then yes, other than that no.

    Sent from my iPad using Tapatalk
  3. squirrel
    Joined: Sep 23, 2004
    Posts: 48,314


    it's likely to slip....
  4. Johnny Nitro
    Joined: Sep 28, 2005
    Posts: 60

    Johnny Nitro
    from Chicago

    Maybe an hour? 20 miles, or so. All I’m running is a fan, and alternator.

  5. 41rodderz
    Joined: Sep 27, 2010
    Posts: 5,390

    from Oregon

    It is easy for us to say yes or no . Go with your gut ,unless you are always wrong.:eek: Put it on, tighten it up and rev the engine and see what it does then decide.
  6. chicken
    Joined: Aug 15, 2004
    Posts: 164

    from Kansas

    If the 1/2" belt doesn't bottom out in the 5/8" pulleys' grooves it'll do just fine. The problem is when the bottom of the belt sits so deep it hits and keeps the sides from touching.
    firstinsteele and onetrickpony like this.
  7. 2B0C61CD-FAAB-4FD7-8CC8-58CD28979CC0.jpeg FB27F90B-EFC2-4078-BB81-4697534F5064.jpeg For an hour or 20 miles I would say your ok.
    It will sit to deep in the pulley
    But for an emergency or temp situation try it
  8. 19Fordy
    Joined: May 17, 2003
    Posts: 7,117


    In a pinch for a short distance it's ok to do.

    Fan belts should not ride on the bottom of the pulley. Only on the sides.
  9. Johnny Nitro
    Joined: Sep 28, 2005
    Posts: 60

    Johnny Nitro
    from Chicago

    Thanks for the replies.

    Update: So far, so good. It’s definitely riding on the bottom of the pulley, and not the sides, but it’s not slipping. I think in the long run it will, but for now there is no noticeable difference.
    VANDENPLAS likes this.
  10. Mark Wahlster
    Joined: May 21, 2016
    Posts: 62

    Mark Wahlster

    Bubba Willys jeep guys do it all the time. The Willys engine uses a 5/8" wide belt but when the guys swap an alternator into cause the Gen has gone out or they are converting to 12V they run a std belt so it fits in the alt pulley. Cause they don't know to change the alt pulley.

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