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dirty carb (and plugs?)

Discussion in '40- & 55-Series Tech' started by rusmannx, Sep 6, 2003.

  1. rusmannx

    rusmannx

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    ok, i've been having trouble with the low end torque as some of you know.
    i've got the gap at
    [​IMG]

    and the plugs all look like this
    [​IMG]

    and my carb gets grimey (after what might only be a trip to walmart and back)
    [​IMG]

    and i clean it to look like this (carb cleaner)
    [​IMG]

    if i shorten the gap to .45 will that make the spark more potent?
    i'm running the DUI.
    what do you other DUI guys have your gap set at?
    i'm also always getting black exaust all the time.
     
  2. rusmannx

    rusmannx

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    ok, assuming that #1 is the plug closest to the radiator;

    #1 is the plug in the pic,
    #2 was black, very black
    #3 was less brown than #1; i would call it tan
    #4 was tan like #3
    #5 was pretty brown
    #6 was pretty brown too.

    why would #2 be so black and not the others?

    also:
    when i stamp on the gas and hold it down, it tries to die... then i let off the gas at the last minute and the engine revives itself. (this is when in neutral of course)
     
  3. hammerhead

    hammerhead

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    I don't know about DUI but stock plug gap (per manual) is .040". Your plug color should be tan to light brown.
    What carb is that? I thought you said you had a Q-jet. Sure doesn't look like a Quadra-jet to me. A Q-jet is a 4-barrel, spread bore.
     
  4. rusmannx

    rusmannx

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    ok, i've gapped them all down to .45 to see what would happen.
    all of my plugs then went black.
    then engine would then lag even more when i hit the gas hard (in neutral).

    now i've gapped them out to .55 and there is less lag when i stomp it in the before fashion. i think there is a little put put sound coming from the tail pipe, but the exaust smeels less rich.

    should i go back to the .45 and lean out the carb, or should i stay with the .55 and lean it out less.

    i think also at .55 it feels like there is slightly better torque.
    now that i've blackened the plugs, do i need to go buy new ones or will it burn off?

    yeah i was wrong about the carb too (i'm retarded)
    it's a "GM 2 Jet Rochester" it says right on the top (duh)
     
  5. hammerhead

    hammerhead

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    To set your mixture first verify that ignition timing, dwell, and advance are correct. Then set idle at 690 RPM. Adjust mixture screw to achieve highest idle speed. Readjust idle speed screw back down to 690. Repeat adjustments until speed can no longer be increased by mixture screw. Reset idle speed screw to achieve 650 RPM.
     
  6. rusmannx

    rusmannx

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    are these the two screws?
    which is which?
    [​IMG]
     
  7. Gumby

    Gumby Supamod Staff Member s-Moderator

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    Those are the idle mixture screws. One for each venturi.
     
  8. hammerhead

    hammerhead

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    Those are your mixture screws. They should be adjusted the same amount of turns out from bottomed. Your idle speed screw is the one on the side that cracks open the throttle.
     
  9. rusmannx

    rusmannx

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    got it, i'll go see what i can do
     
  10. rusmannx

    rusmannx

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    fooling with the mixture screw (either or both together) barely makes the engine change... anything.
    this carb must be junk.
     
  11. hammerhead

    hammerhead

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    Maybe you could get the stock setup to go back on. Is it an adapter or what? I might be able to round up a factory setup from a 72 or 73.
     
  12. rusmannx

    rusmannx

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    i assume there is some kind of adapter.
    i think i'm going to try the $13 rebuild kit first and see if that gets me anywhere.

    if not, i'll get back to you on that offer.
     
  13. IDave

    IDave

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    Rochesters were common on FJ40s, for some reason. Don't know why, but I haven't heard anything especially good about them. I would get an AISIN, either new or used to rebuild.