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Carb troubles??? Long read.

Discussion in 'The Hokey Ass Message Board' started by tragic59, Nov 25, 2004.

  1. tragic59
    Joined: Sep 16, 2002
    Posts: 766

    tragic59
    Member

    Should I be able to adjust my flow mixture screws all the way in and all the way out, while the engine is running, WITHOUT changing anything about the way the motor is running??? Seems to me I shouldn't.

    It's a Carter 2bbl on a Dodge 318.

    A couple months back the engine started stalling at idle, once the engine warmed up. I automatically assumed it was a vaccuum leak, so I drove straight to the NAPA and replace all the vaccuum lines on the top of the motor. No luck.

    I asked ont he HAMB, and the consensus was that the carb needed a rebuild, as it probably had a blocked idle circuit.

    I rebuilt the carb. Twice. Because I still had the problem after the first rebuild.

    I also replaced the cap, rotor, plugs and wires, because I had no idea when the last time that had been done, and I thought it might help.

    During my attempts to 'fix' the problem, the engine developed a terrible miss, and seemed to have gotten worse as I attempted to repair it...

    So, I started thinking, maybe I should work on the points, but I worked some OT at work and had money to burn, so I invested in a Mopar electronic ignition set-up, and installed that instead.

    Again, no luck. Miss was still there, lots of unburned fuel out of the exhauust pipe. So, I figured maybe I got the firing order messed up while replacing the plugs and wires, or installing the electronic set-up. Nope. Firing order was right.

    Time for a compression test. This miss has me thinking I have a dead cylinder or two, or three... Nope again. All cylinders come in between 125 and 150psi. Better than I would have expected.

    But I notice when pulling the plugs, that they all look like their electrodes are made of wet charcoal and smell like gas... At the time I thought, and later confirmed on the internet that this was a sign that the motor was running too rich, and the plugs were wet-fouled... The gap was correct, though, so...

    Wet-fouled after a total of about 45 minutes of run time in the driveway and a test drive of about 3 miles. Must have been VERY, VERY, VERY, VERY rich.

    So I bought some new plugs, installed them and the miss went away along with the unburned fuel out the exhaust.

    I let the motor warn up, adjusted the timing, and started to mess with the mixture set screws. Turns out they were set according to the rule of thumb I've always heard. All the way in and then backed out a turn and a half... But while messing with them, I was able to turn them all the way in and then all the way back out without making any noticable difference in the way the motor runs...

    Seems like this should make a difference, right???

    Is it just time to buy a new carb?

    I would assume that this trouble was caused by ME, because I had never rebuilt a carb before, and I'm kind of a dumbass anyways, but when I was originally trying to diagnose the trouble, the mixture screws were doing the same thing. BEFORED I rebuilt the carb.

    Any ideas.
     
  2. check the float LEVEL[adjustment] and look to see if its holding fuel[maybe a pin hole] and flooding the motor..........
     
  3. tragic59
    Joined: Sep 16, 2002
    Posts: 766

    tragic59
    Member

    I checked/adjusted the float level when I did the rebuild. Both times.

    As for the pin hole, where should I look? Are you saying a pin hole in the floats themselves? I looked at them very closely when I rebuilt the carb. And they weren't holding any fuel at the time.
     
  4. BELLM
    Joined: Nov 16, 2002
    Posts: 2,590

    BELLM
    Member

    Might want to change your oil & filter if running that rich, probably have gas in the oil. Can ruin an engine quickly. Can't help you with the carb. Good luck.
     

  5. JimC
    Joined: Dec 13, 2002
    Posts: 2,241

    JimC
    Member
    from W.C.,Mo.

    A common problem with mopar carbs, is that the screw holding the air cleaner is tightened too tight. The stud on most carbs goes through the top only.
    So, in tightening the air cleaner, the top becomes bowed allowing air to enter the venturi or barrel of the carb.
    To check this, remove the top of the carb and place a straight edge on the mounting surface.
    By rotatating the straight edge around the mounting surface, you should be able to verify if it is bowed.
    If it is bowed, you can straighten by using a vise and plaacing one socket over the top where the stud enters the carb top plate(remove the stud first) then placing two wockets on the out side edges outside edge of the carb mounting surface.
    Squeeze bgently in the vice until a level surface is obtained. Then replace the top of the carb being careful to tighten the mounting screws evenly.
    When replacing the aircleaner, tighten the hold down screw only enough to hold the air cleaner.
    I can not say for sure this is your problem or if this mnethod will fix it.
    With out seeing your car, It is difficult to diagnose.
    Jim
     
  6. Scotch
    Joined: May 4, 2001
    Posts: 1,489

    Scotch
    Member

    Mmkay. If adjusting idle mixture does nothing to impact the way the engine is running, you need help.

    First- double-check the timing advance at 3,000 rpm. It should be at factory spec, which should be around 34-36 degrees on your 318.

    Once this is set, check your initial advance. It should be around 10 degrees. If it's much more, or much less, let us know..

    Once your timing is "perf", lock down the distributor. Now, start it up again, and set your idle. I like to do this with the car IN GEAR. I like it to be as low as it can while maintaining a steady run. On your 318, this could be as low as 750-800 rpm.

    Once you've got a killer idle and the timing is perfectly adjusted, you can fine-tune. I like to disconnect the vacuum advance, plug the vacuum line, and then do my carb adjustments. The vacuum advance is just a helper to what you've already got, so it should be set to run bitchin without it, and then get even sweeter with it.

    So, with your rock-bottom idle and dead-nuts timing, adjust those screws again, and tell me if it makes a difference. If you keep fouling spark plugs, ask the parts guy for the next hotter (higher heat range) plug of the same family.

    Do this stuff, double-check for a vacuum leak at the carb BASE (the most-common place for it to be), and please post your results.

    We'll talk more then.

    Scotch~!-
     
  7. Fatchuk
    Joined: Nov 17, 2002
    Posts: 112

    Fatchuk
    Member

    Makes me wonder just what you mean when you said you rebuilt the carb? when you dissasembled the carb did you soak in carb cleaner to soften up all the gum and shellac that be plugging up the idle circut? Just taking it apart and washing in some varsol will not clean the idle circut it has probably accumulated much hardened blockage that must be cleaned out if it does not do any thing when you turn the mixture jets in and out. tells me that you have a blockage that is not allowing any control of the air fuel mixture..One more thing if I remember corectly those old mopar 318s had major problems with the intake plugging real bad causing an over-rich condition.....fatchuk
     
  8. tragic59
    Joined: Sep 16, 2002
    Posts: 766

    tragic59
    Member

    Thanks for the help guys.

    BellM, good call. I actually bought the oil and filter the day before I started having all this trouble. Still haven't changed it, but I will have to make that a priority.

    JimC, are you saying that the top portion of the carb becomes so bowed that it allows air to enter between it and the bottom portion of the carb? I wasn't entirely clear on that...

    Scotch, I will follow your directions and post results as soon as I can. I'm working 12 hour shifts with an hour commute each way today through Sunday... Maybe Monday will allow me some time.

    Fatchuck, the carb actually looked really, really clean when I rebuilt it. I couldn't find any varnish or blockage of any sort anywhere. I soaked the parts on the first rebuild, but not for more than a couple hours.

    The motor was supposed to have had a rebuild 10,000 miles ago, and the carb must have been replaced or rebuilt at that time.
     
  9. JimC
    Joined: Dec 13, 2002
    Posts: 2,241

    JimC
    Member
    from W.C.,Mo.

    Yes on the top becoming bowed and allowing air to enter between the top and the base casting.

    I worrried with a 68 Plymouth, replaced spark plugs, wires, points, condencer, Dist. Cap, and vaccum advance with no real results.

    I finaly gave in and took it the guru to get him to check dwell, timing and set the carb.

    He could not get any signaficant change, so he calls Steve Ramey, one of our carb genius'
    Steve took one look at it, removed the top, straightened as I outlined earlier, and the car ran like it was supposed to.

     
  10. SKR8PN
    Joined: Nov 8, 2002
    Posts: 439

    SKR8PN
    Member

    Tragic..........
    What YEAR is the 318? and does it still have the ORIGINAL intake on it?
    Reason I ask??
    Somewhere around the late 70's,early 80's,in the beginnings of the emission shit,Mother Mopar had what was called a "foot valve"?? in the bottom of the intake. These had a tendency to burn out and creat a LARGE vacuum leak. Pull the carb,and look STRAIGHT down the holes,to the BOTTOM of the intake.........do you see an opening that looks like something is missing???
    IF SO.....git you a pipe plug and screw it into the hole [​IMG]
    If not...check your brake booster if you run one......
     

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