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Rochester 2gc Carburetor , Rich Right Off Idle,stumble,puff Smoke.

Discussion in 'Early CJ-5 and CJ-6 Tech' started by 70cj5134f, Dec 22, 2018.

  1. Dec 22, 2018
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    616
    This is the stock carb from my mercruiser 3.7.
    I think it's similar to the v6 carb.
    New kit installed after a 4 day dip soak, it's clean.ran a wire, and carb clean spray,
    and compressed air through every passage.
    It starts, idles, runs, and REVS great.
    Right off idle theirs a puff smoke and a hesitation, if u open throttle slow.
    If slam open, it seems ok.
    I've set float 4 different heights, no change.
    I went from 66 to 58 mains, REVS better on top, but no change in puff smoke.
    I found a parts carb on shelf and changed power valve, this cut the puff smoke down,but still their.
    I tried fuel pressure from 2.5 to 4, no change.
    The longer it idles, the worse it smoke puff.
    Looking into carb while running, no fuel dripping.
    Pump squirt seems normal.
    Any ideas?
     
  2. Dec 22, 2018
    Walt Couch

    Walt Couch sidehill Cordele, Ga. Sponsor

    cordele, Ga.
    Joined:
    Mar 29, 2007
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    5,288
    Bad PCV maybe??
     
  3. Dec 22, 2018
    sterlclan

    sterlclan Member Sponsor

    exploring the...
    Joined:
    Feb 21, 2009
    Messages:
    2,755
    the boys v6 did this,timing fixed it. someone wiser than me once said 95 percent of carb trouble is ignition related
     
    mike starck likes this.
  4. Dec 22, 2018
    Rich M.

    Rich M. Shoe pusher

    Maryland
    Joined:
    Mar 23, 2008
    Messages:
    466
    I ponder if you have a vacuum issue, distributor not advancing quick enough.
     
  5. Dec 23, 2018
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    616
    No pcv on this engine, valve cover vent to breather , hose only.
    No vac on dist, Mechanical advance only.
    Ill play with the timing tomorrow.
    And I forgot to mention, the hotter it gets, the better it gets.
    I have no heat (water) in intake manifold yet.
    Even after 30 min of run time, I can lay hand on intake, it only warm.
    I once let it get almost to 220 before I turned on the fan, stumble almost went away.
    Might play with the advance springs, if changing initial doesn't help?
    I'm working on plumbing for heat to intake.
    Air screws set bout 2 out. (Fastest idle).
    Some of the HAMB guys recommended a different dist ,with vac advance(for mpg).
    Ps-what main jet u v6 guys running, and which cfm carb do u all have?(Had 66, 58 in now).
    I may need to go leaner? My carb is the 435cfm(500 equivalent).
     
  6. Dec 23, 2018
    jpflat2a

    jpflat2a what's that noise?

    Riverside CA
    Joined:
    Jul 30, 2003
    Messages:
    7,690
    I think 51 were factory for V6.
    49 and 47 high altitude.
     
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  7. Dec 23, 2018
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    616
    Thanks, I'm going to try leaner? 52 or so.
    Well I never would have thunk it, but I let it run off and on bout 45 min.
    Intake got warm to touch, stumble and smoke went away?
    I'll hook up the hot water intake hoses soon.
    Played with timing, no difference.
    Left it bout 10 btdc, stock is 8.
    Starts warm with bump of key, no squirt.
     
  8. Dec 23, 2018
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member Sponsor

    Denver, CO
    Joined:
    Jul 18, 2013
    Messages:
    1,836
    agreed...lean it out a bit a see what happens
     
  9. Dec 25, 2018
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
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    616
    Filled a couple mains last night with JB.
    I'll ream to bout 50 and try, then enlarge until it's right, then order 2 new mains.
     
  10. Dec 27, 2018
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
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    616
    Home reamed 51s in.
    Hot water hooked to intake.
    Warms up in bout 5 min now.
    Seems to rev better and after 5 min run, no smoke or stumble.
    Might need 52s, had 1 lean pop when revving.
    From 66 stock to 52s , seems like a lot.
    Tuning for a prop vs tuning for a tire, big difference.
    Thanks.
     
  11. Dec 27, 2018
    jhuey

    jhuey Michigan Jeeper! Sponsor

    Indian River...
    Joined:
    Apr 9, 2004
    Messages:
    412
    That Mercarb flows very well. Your on the right track in dialing it in. It was running too fat, lean it down. I am a certified Mercruiser technician, boats do need a lot of fuel to get the job done. I always explained it by saying a boat is like a truck towing a trailer up hill all the time. If it lean sneezes go ahead and open it up slightly. Get it up to temp and run it hard for a couple miles and do a throttle chop and read the plugs. Adjust as needed. I’ve always liked the Mercarb, a little harder to tune in, I have the Holley 360, it has many more variables to aid in tuning in.
     
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  12. Dec 28, 2018
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
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    616
    How do I lean the idle and just off idle? (Air screws 2 out, fast idle).
    I've read bout drilling holes in throttle plates?(but this has stock cam).
    Can't test drive yet, still on engine cart.
    Acts like idle jet too large, but no replaceable idle jet?
    Or the power valve opening too soon?
    And yes it flows some fuel, takes bout a gallon each time I start it and run 30 min, mostly idle.
    Plugs beginning to look better less black, and tailpipe starting to grey.

    20181216_170846.jpg
     
  13. Jan 12, 2019
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
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    616
    After much research I ordered a new power valve, installed and slight
    Improvement, but it didn't go away.
    Read a lot bout these carbs on 2barrel class dirt cars,with a large cam all had holes
    in butterfly. For a stock engine this has a large cam, so I put a 1/8in hole in,
    Wow, what a difference,stumble gone when warm, plugs beginning to tan, they were
    sotty blk.
     
  14. Jan 12, 2019
    Oldriginal86

    Oldriginal86 Member

    Pasadena, Md.
    Joined:
    Nov 5, 2014
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    395
    Glad you got it running right. Were all waiting to see this in the jeep and a video test drive. Or a dyno test.
     
  15. Jan 12, 2019
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
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    616
    Not going to start install til end of March or April.
    I need the cj for farm chores and firewood hauling.
    And don't want to miss any playing in the snow.
    Wish I had a spare t90 to play with fab work.
    I'm trying to locate one to borrow for mock up.
    For now still trying to work out all bugs.
     
  16. Jan 12, 2019
    jhuey

    jhuey Michigan Jeeper! Sponsor

    Indian River...
    Joined:
    Apr 9, 2004
    Messages:
    412
    Looks like you are going to be the MerCarb pro around here. It really starts to come to life on 5.0l. I have seen it used on circle tracks on SBC.
    Great job so far.
     
  17. Jan 12, 2019
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
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    616
    Hate to be a dumbass hillbilly, But what's( 5.0l. ) ? That's a mustang,(or a cop), to me !
    Thanks
    My friends think I'm absurdly nuts, pulling a carb 20 times to get it
    Perfect, when 1st time after kit, they would have benn done.
    I want it crisp as FI!
    Sometimes I get it?
    I don't do upholstery (unless it's a pre sewn kit), but anything else, on a car , I've done or ant afraid to try?
     
  18. Jan 16, 2019
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
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    616
    Ok, new problem, #4 running hotter than rest!
    I'm sure it's cause the pcv suction line is directly behind #4.
    So I'm plugging it and drilling and tapping one 1/8 NPT .
    Locating in center should spread the lean air out?
    Started up last night after dark, pushed cart half out door for ex to escape.
    #4 glowing light orange in bout 15 min.
    Rest same, no glow?
    Before I try rejet (don't think I need to, plugs still brown grey), I'm running it with cleaned plugs , after I've moved. Vac to center.
    15476850690182127448530.jpg
     
  19. Jan 22, 2019
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    616
    It worked, all tubes same color now.
    The vac port next to 4 was feeding it air, leaning it out.
    Vacuum port in center should distribute closer to equal now.
    Pcv system done.
    Now I'm going to rework the advance curve.
    More initial, it likes 10-12btdc at idle.
    Stiffer spring on 1 weight to slow mechanical advance a bit.
    Then limit total to around 30-32.
     
  20. Jan 24, 2019
    70cj5134f

    70cj5134f Member

    East Tn
    Joined:
    Aug 18, 2018
    Messages:
    616
    Stock advance.
    Inital-4-8btdc
    Starts in bout 11-1200rpm
    Total- 34-36
    After mods.
    Initial 12-13btdc.
    Starts in 15-1600rpm.
    Total- 30-32.
    I put 1 slightly stiffer spring on advance weights.
    Lightened weights a tad.
    Put a limit bushing on mechanical advance limit pin.
    Hopefully no detionation!
     

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