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Fouled plugs on the right bank

Engine Issues

  1. 6 pac

    6 pac Member

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    I keep getting a couple of fouled plugs on start up on the right bank of a 340 six pack t/a. It happens on cold start up and if I clean them it will run fine. Everything is stock but I have the revnnator box and have the vac advance disconnected. The motor is all rebuilt and runs perfect other than that. Can anyone help?
     
  2. AUSTA

    AUSTA Well-Known Member

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    Sounds like too much fuel on startup or idle.
    I have found the new Champions RC12YC seem to foul a lot easier & wont clear unless cleaned than the old ones
    The NGK plugs seem to work longer with over fueling.
     
  3. moparleo

    moparleo Well-Known Member

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    How long have you been running this six-pack set-up? Why do you have the vacuum advance disconnected ? Who balanced and adjusted your carbs ?
     
  4. Adam

    Adam Well-Known Member

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    Could the intake gasket on that side allow oil to be sucked in from the lifter valley
     
  5. moparleo

    moparleo Well-Known Member

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    Didn't say if the fouling is oil or fuel. Black or blue/grey smoke ?
     
  6. 6 pac

    6 pac Member

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    The plugs are black fouled. And only at start up. I can clean them and they work fine. And only when the car sits and it's a cold start up. I'm wondering if that heat exchanger has something to do with it. The plugs are super clean after it warms up it's fine but only that start up
     
  7. 6 pac

    6 pac Member

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    Everything has been restored on this car, carbs, heat exchanger, everything and is in perfect working order but this fouling issue.
     
  8. Steve340

    Steve340 Well-Known Member

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    The standard spark plug for iron heads is Champion N9Y
     
  9. moparleo

    moparleo Well-Known Member

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    If it is just one bank that does it, it has to ben carb related. Take out the metering block on the center carb and after removing the power valve and mixture screws, blow it out with an air hose and reinstall it. Readjust the idle mixture screws and see what happens.
     
  10. aussiemark

    aussiemark Well-Known Member

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    If the heads are not a matched pair the RH one may have excessive valve guide clearance or no/worn stem seals allowing oil into the chamber when shut down and fouling those plugs on start up.
     
  11. moparleo

    moparleo Well-Known Member

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    He says they are "black" fouled.. More than likely excess fuel not oil, Seals normally a puff of grey/blue smoke at start up and will clear up quickly. Guides will smoke constantly.
    Pull the dipstick and sniff it. Any fuel smell ?
     
  12. AUSTA

    AUSTA Well-Known Member

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    Try removing the air cleaner slowly open the butterflies before you start it & have a look with a torch to see if there is wet fuel sitting in the bottom of the manifold
    The carby may have the float level a bit to high or there is fuel leaking when the car is stationery
    Do you need to pump the pedal to start or does it start instantly with black smoke could also be the choke set a bit too closed when cold.
     
  13. cudabob496

    cudabob496 Member

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  14. moparleo

    moparleo Well-Known Member

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    For us North Americans, when AUSTA says to use a "torch" to look down the carb with, He is talking about a "flash light". Just FYI.
     
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  15. AUSTA

    AUSTA Well-Known Member

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    That's the one we don't want to set the vehicle alight.