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Spark Plug Fouling Right Vs Left Bank

Discussion in 'Early CJ5 and CJ6 Tech' started by FinoCJ, Jun 23, 2017.

  1. Jun 23, 2017
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
    Joined:
    Jul 18, 2013
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    I am getting significantly different plug fouling on the right vs left bank. The left (driverside) bank runs much leaner than the right. I've leaned the jets down to 48s right now (remember I am at over 5000' here in Denver and drive 5000-12000'), and the left bank seems to be spot on - I get a light grey color and the plugs are nicely clean, even after a mix of driving conditions and wheeling and ranging from my house at 5,000 to over 10,000 and back. But the right bank shows heavily black sooting indicative of very fuel rich - its a dry carbon sooting (no wetness or oil). The right bank has seemingly always been richer than the left bank since the rebuild and as I have slowly gone through the carb and turning process. I think the 48 jets are spot on based on the left bank, but need to figure out what is going on with the right bank.

    The 225 is 60 over with new comp cam (252 grind), original intake manifold, and 2g carb that has been taken apart, cleaned, new gaskets, main jets, PV, accel pump, and idle mix screws. Basically, I am trying to determine if this might be a carb issue feeding unequal amounts of fuel into the manifold, a spark issue, a manifold issue (such as a leak?) or something more internal (cam lobes - although its not a single cylinder, its the whole right bank). Although its more of a secondary issues, plug 6 is always slightly less sooted than 2 and 4, but all 3 still indicated way too fuel rich. Driving wise, this issue is not noticeable unless at high elevations (say over 9,000') and its starts to show indicators of being too rich such as a rougher idle, occasional weak or mis fire, and more fuel smell out of the exhaust. Kind of stuff that seems pretty typical of high elevation change with carb. After 500 miles or so, the right side soot starts to cause a bit more consistent noticeable misfire at idle.

    TIA!
     
    Last edited: Jun 23, 2017
  2. Jun 23, 2017
    Walt Couch

    Walt Couch sidehill Cordele, Ga. 2024 Sponsor 2023 Sponsor 2022 Sponsor

    cordele, Ga.
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    What is your ignition system?
     
  3. Jun 23, 2017
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    Pertronix ignition with their 'flamethrower' coil (internal resistor).
     
  4. Jun 23, 2017
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Hills of NH
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    I knew a guy once with a Hemi that never ran right, turned out to have a high-compression head on one side, low-compression on the other. Just a thought.

    "Since the rebuild" may be the important words here. I personally had a Triumph motorcycle engine return from the rebuilder with a head that definitely wasn't the one I sent in...
     
    Last edited: Jun 23, 2017
  5. Jun 23, 2017
    colojeepguy

    colojeepguy Colorado Springs

    At the foot of...
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    I don't think it's carb....the intake manifold is a dual plane design, each barrel of the carb feeds two cylinders on one side and one on the other.
     
  6. Jun 23, 2017
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

    Tantallon, Nova...
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    What setup is your exhaust?
     
  7. Jun 23, 2017
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    oem manifolds on each side into a y-pipe with single muffler/exhaust exiting rear.
     
  8. Jun 23, 2017
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    Have you done a compression check?
     
  9. Jun 24, 2017
    william_cj3b

    william_cj3b 3BOB driver

    Milton, FL
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    Nov 17, 2003
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    How is the y-pipe configured? Is the Y a narrow angle merging of the two pipes, or is it more of a T? My F100 had a y-pipe that was literally a T when I bought it. Ran like :poo:.
     
  10. Jun 24, 2017
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    Jul 18, 2013
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    The 'y-pipe' is more of a 'T', but its been that way for 4 years with no problems previously. Its probably not the best set-up for maximum flow but it works, its tucked up and out of the way pretty well, and its quiet (which is what I really wanted after the headers and glass packs from PO).

    But now you got me thinking....I had some issue when I got the manifolds, they are not a matching set, and one side has slightly smaller ports (probably a true 225) and the other slightly larger (maybe 231). Wonder if the smaller ports are on the passenger bank and causing some issues when compared to the driver side. Never noticed before, but it was an old and worn engine.
     
  11. Jun 24, 2017
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    No - maybe I can do that this week.
     
  12. Jun 24, 2017
    william_cj3b

    william_cj3b 3BOB driver

    Milton, FL
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    Can you post a picture?
     
  13. Jun 28, 2017
    cayenne

    cayenne Member

    central Texas
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    I don't know if you have checked this, but I had the opposite problem with my passenger bank being much sootier than my driver bank. It ended up being that I had my number #1 hooked up wrong on my oddfire distributor cap and I never knew it until I read this string. where does #1 go( said in a austin powers voice)
     
  14. Jun 28, 2017
    tarry99

    tarry99 Member

    Northern California
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    Do a leak down on those cylinders........did you do the valve guides & put guide seals on those heads?
     
  15. Jun 28, 2017
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    I believe Fino is saying his passenger bank is the sooty one also.
     
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