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How to Tighten Belts - 87 Fifth Avenue

Interior and Electrical

  1. Justwondering

    Justwondering Well-Known Member

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    This is a basic question which I can't see to find an answer for in the service manual. Most of the videos online assume a tensioner pulley is in the mix.

    I rerouted my heater hoses so they are correctly positioned.

    I checked the belts and they seemed to have play in them. To tighten the belts:
    1. I stood at the passenger side fender
    2. Leaned over and used my left hand to grab the underside of the alternator
    3. Used my right hand to loosen the 1/2 inch bolt at the top bracket of the alternator
    4. Gave a mighty pull with my -non-popeye left arm
    5. Quicky tightened the 1/2 inch bolt with my right hand

    There is still play in the belts, just not as much.

    How do you properly tighten the belts? and
    How do you know when you have them tight enough?
     
  2. rcmaniac791

    rcmaniac791 Well-Known Member

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    The alternator does act as the belt tensioner for those 2. I've always done the same thing by just grabbing the alternator and pulling. It's not an exact science, but you want them firm. Not rock hard, because that can prematurely wear things out. Typically, I go for half an inch to an inch of movement MAX. It should also take a reasonable amount of pressure to really move the belts. Another test is to rev the engine real quick, and if the belts don't slip and squeak, you're probably good.
     
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  3. Aspen500

    Aspen500 Well-Known Member

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    That's exactly right 791.
    Usually checked on the longest span between pulleys, there should be no more than 1/2" of deflection with REASONABLE force. Anymore and it's too loose and if there's less than 1/4" deflection it's too tight.

    I've seen belts overtightened that actually caused the upper main crank bearings (especially the front one) to wear big time. The belt was always pulling up on the crank pulley. Mostly saw that on old Ford 302/351 of the late 1970's and early 1980's. Usually too tight belts will cause the water pump or alternator bearings to fail.
     
  4. BudW

    BudW Moderator Staff Member

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    They make an official tool to make tightening the alternator belt easier.

    Justwondering, you are almost right on, except I like to add another step.
    On the front of alternator, there is two bolts, ½” and 9/16” heads. The ½” head is what holds the belt tension. I recommend loosening the 9/16” head bolt a bit first, which helps the alternator pivot easier.
    Then pull the alternator, tighten the ½” head bolt first, then lastly tighten the 9/16” head bolt to finish.
    You will find it easier to pull on and easier to get it to the correct tension.

    I will take a picture of the official tool, when I get home – but you don’t have to use one.
     
  5. Justwondering

    Justwondering Well-Known Member

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    I'm so not official .... lololol
    I'll go try loosening the pivot bolt first and then the 1/2 inch bolt before I pull it.
    Its been raining over 4 hours so it will wait til manana.
     
  6. Master M

    Master M Well-Known Member

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    I have read you don't want anymore than 1/2" to 3/4" of deflection with 5 pounds of force.
     
  7. 80mirada

    80mirada Well-Known Member

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    I have a hook that goes around the alternator. They used to make a threaded spreader that went between pulleys, and there was a funky specially bent pry bar for adjusting the alternator belts
     
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  8. lowbudget

    lowbudget Well-Known Member

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  9. 80mirada

    80mirada Well-Known Member

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    That Lisle one is what I have.
     
  10. BudW

    BudW Moderator Staff Member

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    That is the same one I have, as well.

    I have used the “official belt tensioner gauge” but found it to be cumbersome to use and all in all – not user friendly.
    So far driving cars for 35 years (longer than that unofficially), have tightened hundreds of fan belts without one, and been fine.

    I kinda forgot to take a picture when I got home last night (at 8:30pm).

    My plan was to take a picture of the tool and of a loose Chrysler alternator I have - to show where to pry on it at.
    If you use one of the fins, you will end up breaking off that fin.
     
  11. Darth-Car

    Darth-Car Well-Known Member

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    Yep, first alternator belt I did on a Chrysler, I jammed a long handled screwdriver in the alternator fin, and pulled the thing tight. Then after a couple of minutes I get "KKAAA-TING", screwdriver, and fin both fell to the ground. Decided that was a bad idea. Oh what we do in our youths.
     
  12. BudW

    BudW Moderator Staff Member

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    The moment you KNOW what you did wrong . . . before you saw the damage.
     
  13. volareandgtcat

    volareandgtcat Well-Known Member

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    My time was with a broom handle .. got er good and tight ... south side of Chicago on our way back from LA and the battery finally gave out .. the alt. bearing was shot .. lucky it was the late 70's and things weren't as bad .. even found an honest mechanic that did the job for less than what I expected .. you know ... being in the middle of nowhere without a paddle n stuff .. oh yes our younger years ... lol ........... now only the memories .. and only when prodded .. lmao ........ justwondering ... not too tight .. it's not better .. make it just right ... lol
     
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  14. Justwondering

    Justwondering Well-Known Member

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    The hood sits so much better now. Still a little wonky on the passenger side, but now its low on the driver's side. Gives me plenty to work with. I'll go undo my earlier efforts on the passenger side and see if it all sits better.
     
  15. Justwondering

    Justwondering Well-Known Member

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    IMG_5537.jpg
    The above picture is how I had the heater hoses after I completed the new hoses my first time. Everyone of them running over the top of the compressor was pushing against the underside of the hood or heating the cooler lines. Not good.

    After a couple of hose shots from BudW, here is how I changed things.
    IMG_5539.jpg
    Changed the one hose to run under the compressor and the other to go to the backside.

    Now I need to re-adjust my hood. lol. I should have looked at my original photo and done it that way (like this). Here I was thinking,
    'I'll just move these things around so I can get to them easier next time'... no,
    they are in there in a specific way for a specific reason. Learned my lesson.
     
  16. BudW

    BudW Moderator Staff Member

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    Thumbs up!

    A picture (or a bunch) beforehand, as well as picture(s) of parts (and fasteners) as they are being removed, helps: (fill in the appropriate answer)
    (a) keep ones hair in place longer,
    (b) keeps the frustration level down,
    (c) from rediscovering those four letter words you thought you worked out of your system,
    (d) finding out how many ways the jigsaw puzzle doesn’t go together,
    (e) keeps the dog (or cat, or fill in the blank) from getting kicked, or
    (f) all of the above.
     
    Last edited: Sep 6, 2016
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