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F134 Belt Setup

Discussion in 'Early CJ-5 and CJ-6 Tech' started by kenb, Feb 9, 2019.

  1. Feb 9, 2019
    kenb

    kenb Member

    Detroit
    Joined:
    Jan 22, 2019
    Messages:
    104
    Hello,
    I have a M38A1 with what I think is a civilian F134 engine. It has a 12v system with an alternator installed. When the previous owner bought the jeep it didn't have the fan on the engine. It had an electric fan in front of the radiator. He purchased and installed a fan on the engine. However, it appears the fan belt cannot be tightened. The fan spins but the belt is loose and noisy.
    IMG-20190209-WA0010.jpg
    IMG-20190209-WA0007.jpg

    There appears to be a double pulley on the crankshaft. I'm thinking it might be of the type for an external governor? My thoughts are to acquire a larger pully for the alternator and move it forward a bit and run both accessories on a single belt. Am I missing anything? Does anyone have any suggestions?

    Thanks,
    Ken
     
  2. Feb 9, 2019
    65seejayfive

    65seejayfive Blazin’ new trails

    York, PA
    Joined:
    Apr 10, 2018
    Messages:
    258
    On my F134 I have one belt: My alternator, water pump/fan, and crank pulley. I adjust tension in the slotted arm that the top of my alternator is mounted to. I would do as you say and move your alternator front so that you can run on a single belt. Could you flip it around to the front side of the arm? My crank pulley has two grooves as well but I am only using one.
     
  3. Feb 9, 2019
    Glenn

    Glenn Kinda grumpy old man Staff Member Sponsor

    Apopka, Fl
    Joined:
    Sep 21, 2002
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    You have the correct idea for the fan belt, you are describing the proper setup. The proper belt is also 5/8" wide.
     
  4. Feb 9, 2019
    65seejayfive

    65seejayfive Blazin’ new trails

    York, PA
    Joined:
    Apr 10, 2018
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    What is the reasoning behind the double pulley on the crank anyway? Just curious.
     
  5. Feb 9, 2019
    kenb

    kenb Member

    Detroit
    Joined:
    Jan 22, 2019
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    104
    Thanks for the replies. I have a correct belt on the way. Given some time tomorrow I'll take a closer look at that alternator mount and see if I can move it forward. I understand the correct belt is 5/8". Is that also the inside with of the pullies? I should check the crank and fan pullies to make sure they are the correct size and also order a correct one for the alternator.

    I'm thinking the crank pully is from this type of setup. Does that sound correct?
    Governor setup_1.GIF
     
    65seejayfive likes this.
  6. Feb 9, 2019
    Glenn

    Glenn Kinda grumpy old man Staff Member Sponsor

    Apopka, Fl
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    Sep 21, 2002
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    That's my understanding.
     
  7. Feb 9, 2019
    PeteL

    PeteL Member Sponsor 2019 Sponsor

    Hills of NH
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    Aug 3, 2003
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    6,262
    Double pulleys all round and ("matched") twin belts were the M38A1 set-up.
     
  8. Feb 9, 2019
    baldjosh

    baldjosh Sponsor Sponsor

    pacific north west
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    Oct 24, 2017
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    247
    I just installed my alternator a week or so ago...I used brackets and a pulley from Willys Works in Arizona. pretty straight forward set up. im very happy with the parts!
    The stock belt may require a bigger pulley on the alt.
    20190209_144205.jpg 20190209_144241.jpg 20190209_144313.jpg
     
    ITLKSEZ likes this.
  9. Feb 9, 2019
    Keys5a

    Keys5a Sponsor Sponsor

    Joined:
    Jan 23, 2014
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    If your were to find an M38a1 double fan pulley, that would be the easiest solution. Then if you found a double alternator pulley, you could even run the correct pair of belts.
    -Donny
     
  10. Feb 9, 2019
    Howard Eisenhauer

    Howard Eisenhauer Super Moderator Staff Member Sponsor

    Tantallon, Nova...
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    Just to be clear the mil double pulley & civilian are different from each other- on the civvy version the rear one for the governor is narrower than the front water pump/genny part. On the military they are as mentioned both to drive the genny & are the same width.
     
  11. Feb 11, 2019
    gunner

    gunner Member

    Washington state...
    Joined:
    Dec 4, 2012
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    585
    Your current set up has no way to adjust or tighten the fan belt. Unless there is something I'm not seeing there, you'll never get it to work.

    As some of the others mentioned, the M38A1 had double pulleys on crank, fan/water pump and generator. It was a heavy duty set up. On my A1, the PO changed it to 12 volt but kept a double pulley for the alternator.

    If you don't want to move your alternator out, you'll need to get an M38A1 double pulley water pump. Find it on ebay, 1/4 Ton Military has them. It sounds like they are quality, US-made parts and should solve all your problems. Avoid the omix stuff even if it's a few bucks less.
     
  12. Feb 11, 2019
    Alan28

    Alan28 Well-Known Member Sponsor 2019 Sponsor

    Châtillon en...
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    Here we see how this forum is the best one...
     
    ojgrsoi likes this.
  13. Feb 11, 2019
    kenb

    kenb Member

    Detroit
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    Jan 22, 2019
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    104
    Thanks for all the replies. I ended up getting a larger pulley for the alternator and moving it forward to be in the same plane as the water pump. I'm running one 5/8" belt. Seems to be working so far.
    Upon closer inspection I think the crank pulley is the large/small combination for a governor. So using the forward pulley with a large belt works.
     
    baldjosh and Glenn like this.
  14. Feb 12, 2019
    1960willyscj5

    1960willyscj5 Well-Known Member

    Mesa, Arizona
    Joined:
    Nov 27, 2006
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    2,792
    Or rig up a belt tensioner like the one in the caravan V-6.

    Probably picik one off of any after 2000 car or pickup. or van.
     

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