Fuel smoke and fouled plug

Big Block A body Tech

  1. Nick I

    Nick I Active Member

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    Alright FABO.

    67 Barracuda 383 4 speed.

    Chasing my tail here. I have white smoke coming from the passenger side exhaust. Definitely unburned fuel.

    My number 8 cylinder keeps fouling the plug. Looks like due to inefficient burn. I’m thinking bad plug wire or it’s because the distributor has no vacuum advance hooked up. When it is hooked up it runs like garbage at higher RPM. I have an electronic distributor waiting to go in until I can buy replacement wiring harness and upgrade the voltage regulator.

    Motor was ‘recently’ rebuilt several years ago but never ran or broken in until the guy I bought off of broke it in. Compression and leak down were in line for what a fresh motor should be. Less than 10% psi difference between highest and lowest on compression and only 6% loss during leak down. #8 cylinder performed at the top of the class for what it’s worth.

    Any insight would be greatly appreciated!
     
  2. fishmens67

    fishmens67 Well-Known Member

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    white smoke usually indicates water.
     
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    • Nick I

      Nick I Active Member

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      Understand that totally but this is definitely not water. It smells like extremely rich exhaust, no sweet coolant smell. Also, no bubbles in the coolant during leak down and spark plug is black/brown not white. As far as my understanding goes, those are all the indicators for bad head gasket or cracked cylinder. If I’m off though let me know. Like I said I’m chasing my tail.
       
    • 67Dart273

      67Dart273 FABO Gold Member FABO Gold Member

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      Advance would not affect only one cylinder like that. Bad plug / bad plug wire/ carbon tracked/ cap cap might, but that is easy to "try."

      You can not go by bubbles in coolant.
       
    • Nick I

      Nick I Active Member

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      I may try new plug wires since that’s what my budget can handle right now. I did a resistance check and all plugs were about where they should be ohms/length speaking.

      Cap, rotor appear to be brand new. Haven’t checked the dwell spots that could be a cause too I think?
       
    • Northern Grit

      Northern Grit Well-Known Member

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      Just throwing an idea out there but it could be oil fouling like from a dislodged intake valve seal.
       
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      • Nick I

        Nick I Active Member

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        If it helps, here is a picture of my passenger side plugs after about 40 minutes of run time. Number 2 looks a bit dark too but not like 8.

        B5FF7F78-4940-4E2A-8BD2-8DCAC4B2CCA7.jpeg
         
      • Nick I

        Nick I Active Member

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        Very well could be. Haven’t cracked the cover yet.
         
      • DrCharles

        DrCharles Well-Known Member

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        Another possibility is an oil leak into #8 intake port from the underside of the manifold. Have you checked the gasket/seal there?
         
      • Nick I

        Nick I Active Member

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        I do have a small vacuum leak near the heat sync area of the intake. Based on that leak, it’s a good bet you’re right. I’ll be replacing the gaskets this weekend.
         
      • jaws

        jaws I put the fun in dysfunctional FABO Gold Member

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        Swap a plug hole to hole and a plug wire see if it changes. Change out the intake gasket, need a good seal to trouble shoot further. Where in Colorado?
         
      • Nick I

        Nick I Active Member

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        Im in the Brighton area. Will be doing the intake gaskets this weekend and I’ll try the plug and wire swap after. Great idea.
         
      • jaws

        jaws I put the fun in dysfunctional FABO Gold Member

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        Not to far from you, Strasburg. Let us know how I works out.
         
      • Nick I

        Nick I Active Member

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        not too far at all! I’m swapping the intake gaskets this weekend and will re-tune the timing and carb. I also discovered that I’m missing the second ground strap from the passenger head to firewall. So need to take care of that and get a new plug for the fouled one. Then we will go from there ha ha!
         
      • fishmens67

        fishmens67 Well-Known Member

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        what heat range plug are you using.
         
      • Nick I

        Nick I Active Member

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        5. using NGK 3332.
         
      • Nick I

        Nick I Active Member

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        Small update. Got the valve covers and manifold off this morning. Good news is I have 915 heads. Bad news is whoever put this thing together used a super thick aluminum head gasket. Not bad on its own but when they put things together the extra space cause the valley pan and gasket to be misaligned. They also had a lot of permatex ooze out into the intake channels. From what I can tell this was causing both an air leak and possible picking up oil when accelerating hard. I’ll be putting it all back together (correctly) this weekend, put a new plug into #8 and maybe #2 and drive her for a while and see if things clear up at all.
         
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        • 67Dart273

          67Dart273 FABO Gold Member FABO Gold Member

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          ^^That would be enough to do it!!!^^
           
        • Nick I

          Nick I Active Member

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          Like, a lot of permatex!
          C9E9AC8D-F533-4E77-8E09-C983B779D5F9.jpeg
           
        • jaws

          jaws I put the fun in dysfunctional FABO Gold Member

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          SE if you can find a set of fiber gaskets to use with the valley pan.
          Think you might have found your issue.
           
        • Nick I

          Nick I Active Member

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          Fiber gaskets in hand. Two per side. Only need a smear of permatex on each one where it meets the valley pan right?

          I’ll have to put a thicker bead down at the front and rear because of the fancy head gaskets but the pan should flex.
           
        • AJ/FormS

          AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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          Are you running a dual plane? If yes, then,Check the two center plugs on the other side and compare to 2 and 8. If they are all on the same side of the carb, maybe it means something,IDK.
           
        • Nick I

          Nick I Active Member

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          Drivers side bank is all good as far as plugs go. I really think based on the permatex ‘reduction’ and the vacuum leak, and the oil straw, that’s where all of my issues are coming from. Hard to say otherwise until that’s all fixed.
           
        • jaws

          jaws I put the fun in dysfunctional FABO Gold Member

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          pan down like normal, then the fiber gaskets has worked well for me.
           
        • Nick I

          Nick I Active Member

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          Update #2

          New intake gaskets got me up to 14 lbs of vacuum. At my altitude that’s right where it should be.

          The smoke is still there, but is now 100% burning oil. First start up there was a slight bit of smoke. Shut it down to take the vacuum gauge of and put the air cleaner on. Started it back up thinking I was going to take it for a drive and had much heavier blue smoke. #8 plug is pitch black, no more shiny to it.

          Im almost certain it’s a bad valve seal, unless anyone can think of anything else?
           
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