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High Altitude Carb Jetting?

Discussion in 'Early CJ5 and CJ6 Tech' started by Douglas C Box, Aug 28, 2006.

  1. Aug 28, 2006
    Douglas C Box

    Douglas C Box New Member

    Prairie Village...
    Joined:
    Mar 15, 2003
    Messages:
    34
    Older CJs with carbs have a tendency to load up when ran in high altitude trails in Colorado. Anyone ever heard of what jet size to use when re jetting the F134 engine? I would like to get a little better running engine un there on those high trails! Doug
     
    Douglas C Box, Aug 28, 2006
    #1
  2. Aug 28, 2006
    panzer

    panzer Super Mod Staff Member

    Columbus, OH
    Joined:
    Dec 9, 2003
    Messages:
    1,245
    panzer, Aug 28, 2006
    #2
  3. Aug 28, 2006
    jpflat2a

    jpflat2a what's that noise?

    Hermosa, SD
    Joined:
    Jul 30, 2003
    Messages:
    8,525
    as far as I recall, the YF on the F4 uses a metering rod to compensate for high altitude (richer/leaner)
    There were 2-3 listed in the factory parts manual; availability unknown now, probably nada.
    you can always lower the float level/install in-line press regulator to control float bouncing on rough roads.
    another possibility would be to advance the timing 5* or so
     
    jpflat2a, Aug 28, 2006
    #3
  4. Aug 28, 2006
    Warloch

    Warloch Did you say Flattie??? Staff Member

    Falcon, CO
    Joined:
    Mar 4, 2003
    Messages:
    5,471
    There won't be a 'magic jet size' - every engine is different. Take what you have if it runs good there and then for every 1500 feet (books say 2,000 but I have found this works better) increase, drop a jet. I usually figure a 'median' altitude to work with. If I am camping or staying at 7500 (base jetting) and going up to 12000 I take the diff (4500 feet) and take 75% of that (3375) / 1500 = 2.25 so I would bump the jets 2 sizes down...

    Clear as mud ?
     
    Warloch, Aug 28, 2006
    #4
  5. Aug 28, 2006
    jpflat2a

    jpflat2a what's that noise?

    Hermosa, SD
    Joined:
    Jul 30, 2003
    Messages:
    8,525
    Chuck
    were jets available for the YFs
    or just the metering rods ?
    what do you do on YFs ?
    for extended stay (2 weeks) I'd do the mods
    not for anything shorter
     
    jpflat2a, Aug 28, 2006
    #5
  6. Aug 29, 2006
    Warloch

    Warloch Did you say Flattie??? Staff Member

    Falcon, CO
    Joined:
    Mar 4, 2003
    Messages:
    5,471
    If I remember, there used to be both - I think I still have some out at the farm... Won't get out there to look for a few weeks though.
     
    Warloch, Aug 29, 2006
    #6
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