Is this carbon buildup? And how can I fix this?

Fuel and Air Systems

  1. 67DodgeDart360

    67DodgeDart360 Well-Known Member

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    My car is running really bad. Does this look like carbon build up? It's all black. The car is making a pop sound when I step on the gas petal. And I can smell something. How can I fix this issue. I have a 360 engine in a 67 Dodge Dart.

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    • Jadaharabi

      Jadaharabi FABO Gold Member FABO Gold Member

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      What is your timing set at?
      Do you have a flat cam lobe?
       
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      • mopar head

        mopar head Well-Known Member

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        Back fire soot, probably can clean with carb cleaner.
        The cause of the backfiring? I`d start @ verifying timing, then valvetrain.
         
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        • Mattax

          Mattax Just the facts, ma'am FABO Gold Member

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          Yup.
          Only way for burning to occur in the intake passages is for something to set off the fuel before the intake valve is fully closed.
          So either valves not closing in time or ignition is too early for that rpm and load.
           
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          • Mtrhead

            Mtrhead Ace of Spades ♠️

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            Timing
             
          • Jadaharabi

            Jadaharabi FABO Gold Member FABO Gold Member

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            Or an exhaust lobe is flat and once the fuel mixture is set off the only place it has to go is back out the intake valve during overlap.
             
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            • 67DodgeDart360

              67DodgeDart360 Well-Known Member

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            • 67DodgeDart360

              67DodgeDart360 Well-Known Member

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              Sounds like it might be a bad lobe. How would I check that?
               
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              • 67DodgeDart360

                67DodgeDart360 Well-Known Member

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                How can I fix this if that’s the issue?
                 
              • inertia

                inertia Well-Known Member

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                Pull the plugs, one will look different.
                Then pull the valve covers looking for a bent pushrod, broken rocker, worn cam lobe, on the cylinder with the "different" plug ..
                 
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              • mopar head

                mopar head Well-Known Member

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                If you had 2 mechanics set your timing, all the investigative work as mentioned above will probably require your 2 mechanics.
                someone here may have the patience to guide you through it.
                 
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                • Jadaharabi

                  Jadaharabi FABO Gold Member FABO Gold Member

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                  Pull a valve cover. Start the engine and watch the rocker arms. If one just wiggles or barely moves then it's flat. If they all rock then check the other side.
                  The fix is a new cam and lifters.
                   
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                  • 318willrun

                    318willrun Utube channel 318willrun

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                    Here is the list, in no particular order:
                    1. crossed plug wires
                    2. timing chain has jumped/valve timing off
                    3. bad cam lobe on the exhaust side
                    4. exhaust valve not opening due a push rod rammed through the rocker, or slipped out, etc
                    5. Ignition timing is off
                     
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                    • MOPAROFFICIAL

                      MOPAROFFICIAL FABO Gold Member FABO Gold Member

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                      Old .509 cam plus stock convertor and 3.23 gear with maybe 10 initial. Reversion. Lol
                      I'll go with the timing as well and backfire..and maybe even pump shot
                       
                    • Jadaharabi

                      Jadaharabi FABO Gold Member FABO Gold Member

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                      As 318wr said a cross plug wire or even a bad plug wire. Had that happen with a new set. Looked everywhere for the miss after a tune up. It was one of the new wires.
                       
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                      • MOPAROFFICIAL

                        MOPAROFFICIAL FABO Gold Member FABO Gold Member

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                        Only 2 listed are even relevant to the sooty carb. He would have to be driving the crap out of it while in that condition to look like that..
                         
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                        • Jadaharabi

                          Jadaharabi FABO Gold Member FABO Gold Member

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                          Post 1, third sentence. It pops when he steps down on it.
                          To me that means a back fire thru the carb. That will build carbon deposits from the cylinder to the air cleaner faster than you can imagine.
                           
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                          • Mattax

                            Mattax Just the facts, ma'am FABO Gold Member

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                            Buy a timing light, a tachometer, and a golf tee.
                            Hook up the tachometer. If your car has a multi-spark CD ignition (such as MSD 6) then you'll need a tach that can work with the MSD tach output or some alternative to the old school types. If there is a tach in the car that works, its not ideal but will be good enough to get you started.
                            Find the timing marks. Clean.
                            Hook up the timing light. Run the wires so they won't get burned or cut.
                            Find the vacuum line running to the distributor. Remove it from the distributor and stick the golf tee in the hose.
                            Start the car and when the engine can be kicked down to slow idle, check the rpm and the timing.
                             
                          • 318willrun

                            318willrun Utube channel 318willrun

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                            Bingo! And all 4 that I mentioned can and will cause a backfire through the carb doing exactly what you said, build carbon deposits.
                             
                          • Mattax

                            Mattax Just the facts, ma'am FABO Gold Member

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                            Oh hell. Look at this.
                            Looks like vacuum advance is connected to manifold vacuum. Red arrows. In many cases that can lead to too much timing at idle.
                            And the port for the vacuum advance timing is capped. Yellow arrow. The cap is dried out and cracked too. H'mm.
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                            Anyway if I'm right, what you do after the first test is take the golf tee out and reconnect the hose. Then remeasure rpm and timing. You'll probbaly see a big jump in both :( But who knows so check it out. Proper way to set initial is with vac advance plugged. Then in most cases with a stock distributor, connect to the timing port (yellow arrow) and cap the manifold vac port.

                            Also not seeing PCV. That also can effect idle.
                             
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                            • MOPAROFFICIAL

                              MOPAROFFICIAL FABO Gold Member FABO Gold Member

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                              that's an Avenger Carburetor those are crap. Bet somebody put a huge pump shot on it to try and cure a lean stumble and on top of that... it might have a light spring on the secondary.
                               
                            • RustyRatRod

                              RustyRatRod Bla de blizhibliz de blatde blizi bla bla

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                              A video of the popping will save a thousand words of description.
                               
                            • MOPAROFFICIAL

                              MOPAROFFICIAL FABO Gold Member FABO Gold Member

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                              Yes but that's not one in was referring to. Again. only 2 out of the list are even relevant.

                              Timing, it's more than likely high initial on manifold vacuum as mattax pointed out.
                              Lean pops can occur with too little pump shot or really high initial lighting it up through the intake manifold.
                              Too much pump shot can make boggy sooty mess as well...and that can catch and back fire too on the extreme end.
                              My advice it to start from scratch on the tune, get the ported vac hooked up, timing/curve right and then tune the transition...if it's bad still, plugs look good and not FOULED then look for mechanical failure of some kind.
                              He was just throwing everything you could at it for reasons to be
                              Happy hunting.
                               
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                              • thesiren74

                                thesiren74 Well-Known Member

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                                2 mechanics setting the timing at what 8° btc? It needs a little more
                                 
                              • MOPAROFFICIAL

                                MOPAROFFICIAL FABO Gold Member FABO Gold Member

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                                On manifold vacuum like it is as soon as he hits the gas it drops down into mechanical timing and it could be really low for all we know depending on the springs inside.
                                manifold vacuum is the half-assed way to high initial timing without actually mechanically altering the advance plate
                                 
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