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Technical Flathead V8 diagnostics

Discussion in 'The Hokey Ass Message Board' started by F-ONE, Jul 3, 2020.

  1. F-ONE
    Joined: Mar 27, 2008
    Posts: 2,105

    F-ONE
    Member
    from Alabama

    The engine in my '51 has a miss or a skip.
    I have gone through all the tune up procedures except confirming time. I'll have to mark the dot as the light did not pick it up.

    It has new properly gapped plugs, new points set to spec, a good set of wires, good cap and rotor.

    The timing light shows the skip.

    The carburetor is a freshly overhauled 94.

    The vacuum gauge reads 20(good engine) in the middle of the green.

    I set the carburetor by vacuum gauge. Out has a very small effect, in it starts to stumble back out it smooths out.

    I had to adjust the idle down a little after the headers were installed.

    The 94 is very cool when it's running and will form condensation on the carburetor body.

    The carburetor bowl does get wet with gasoline, just barely. It's hard to tell if it's the bowl plugs or the top gasket. It does not drip but you can see the moisture on the casting.

    The iron bottom of the carburetor seems to seep a little gasoline but....not a bad leak but it does seem to seep gas a little at the base.

    I have not ran a compression check. Would I need to with the vacuum gauge reading in the green? The needle is dead steady no bouncing.

    You can feel the skip in the exhaust gas coming from the headers. It seems to be more prominent on the driver's side.

    I'm thinking it may need a float adjustment or the carburetor may be dribbling gasoline.

    How do I correct this? What's my next step.


     
  2. 19Fordy
    Joined: May 17, 2003
    Posts: 6,814

    19Fordy
    Member

    Have you hooked up a vacuum gauge?
     
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  3. greybeard360
    Joined: Feb 28, 2008
    Posts: 1,463

    greybeard360
    Member

    Try reading his post all the way thru......
     
    67L36Driver, F-ONE and flatford39 like this.
  4. 19Fordy
    Joined: May 17, 2003
    Posts: 6,814

    19Fordy
    Member

    Ok, I tried again and was successful. Thanks for micro managing.:eek:

    GF-ONE: Could there be a problem with your distributor cap or plug wire terminals not
    fully seated?
     
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  5. wheeldog57
    Joined: Dec 6, 2013
    Posts: 1,685

    wheeldog57
    Member

    F-ONE, let It idle and pull one plug wire off at a time. See if it makes any change. Try and find suspect cylinder then you can diagnose from there
     
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  6. BamaMav
    Joined: Jun 19, 2011
    Posts: 4,151

    BamaMav
    Member
    from Berry, AL

    If the light shows the skip, I'd say it was electrical. Bad connection, bad wire, bad plug would be my guess.I'd start with pulling the wires as suggested to see which cylinder is affected, then replace plug with a known good one, then wire, then look at the cap to see if it's cracked or carbon trailed.
     
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  7. tubman
    Joined: May 16, 2007
    Posts: 4,982

    tubman
    ALLIANCE MEMBER

    I think it's time for you to buy a compression gauge. Information is power.
     
    RMR&C, F-ONE and Desoto291Hemi like this.
  8. F-ONE
    Joined: Mar 27, 2008
    Posts: 2,105

    F-ONE
    Member
    from Alabama

    I’ve got one but it needed a O ring. I have the O ring now so I’ll do a compression test to see what I have.
     
  9. F-ONE
    Joined: Mar 27, 2008
    Posts: 2,105

    F-ONE
    Member
    from Alabama

    I’m going to pull the plug wires as suggested.
    I’m thinking the same thing you are about the skip showing with the light.
    I’m going to check and clean all the connections and do a compression check to see what shows up there.

    Below are the plugs and wires that came off the car. When I got the car it would barely run.
    That’s all been replaced.
     

    Attached Files:

    Last edited: Jul 3, 2020
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  10. F-ONE
    Joined: Mar 27, 2008
    Posts: 2,105

    F-ONE
    Member
    from Alabama

    I will do.
     
  11. F-ONE
    Joined: Mar 27, 2008
    Posts: 2,105

    F-ONE
    Member
    from Alabama

    Thanks,
    I will double check all the connections in the ignition system.

    When I got the car last month it would barely run.

    Not only would the car barely run it would barely crank over and would not crank at all hot. Cleaning all the primary leads made a difference, like night and day.

    Since it’s running fairly well now....
    I realize just how bad it was.
    The sellers said it needed a 8 volt battery and the bad gas burned out of it.
    The connections were horrible with corrosion. No need for an 8 volt, all it needed was the cables clean,
     
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  12. tubman
    Joined: May 16, 2007
    Posts: 4,982

    tubman
    ALLIANCE MEMBER

    +1 on not needing an 8 volt battery. The ultimate "band-aid".
     
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  13. Mr48chev
    Joined: Dec 28, 2007
    Posts: 26,880

    Mr48chev
    ALLIANCE MEMBER

    When you do the compression test make sure that the choke is wide open and prop the throttle wide open to let the air flow.
    ALL PLUGS OUT WHEN YOU DO IT!!! I've run into guys who pulled one plug at a time and checked a cylinder and put it back and pulled the next one and that doesn't work.

    I've always let each cylinder hit 5 times on the gauge on each cylinder and recorded the reading and went to the next. That is what I was taught, did and then taught my students.

    By the looks of those plugs and wires a new set of plugs and wires wouldn't be wasted money.
     
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  14. Fortunateson
    Joined: Apr 30, 2012
    Posts: 3,112

    Fortunateson
    Member

    He already replaced the plugs and wires...
     
    Last edited: Jul 5, 2020
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  15. MantulaMan
    Joined: Jun 19, 2018
    Posts: 37

    MantulaMan

    I would suggest its running lean, when you describe setting the carb you said it stumbles when you wind the screws in. When you set it with the vacuum gauge you should wind the screws out to get the most possible vacuum and stop when your adjustment makes no difference.

    Sent from my SM-A105G using Tapatalk
     
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  16. F-ONE
    Joined: Mar 27, 2008
    Posts: 2,105

    F-ONE
    Member
    from Alabama

    Resolved....

    It was basic stuff.
    Go by the check list.....

    I learned some things...
    It may be possible to tune one by ear but you have to know what a well tuned engine sounds acts like. Even if you do know how it supposed to sound and act ....Tuning by ear is inaccurate at best.

    The timing light does not lie.
    I had a hard time finding the mark with the light. While I was underneath doing the headers, I found the mark...marked it, so I knew what I was looking for. The main reason I had trouble finding the mark is I was looking on the wrong side of the pointer. That first go around I was unfamiliar with what the dot actually looked like.

    How the ear can fool you.....

    That first go around I could not find the mark so....I did it by ear.:rolleyes:
    It was a 12V light on a 6V car and it flickered.....The light flickered with the skip. In a sense ...it was crazy....like the flickers did not make sense. I did not completely trust the light.
    I'll get to the flicker in a moment.

    By ear....
    It's easy to assume that stuff is in the right place.
    Advancing the the time causes it to run rough....that's obvious.
    Retarding the time caused it to do what I thought was loading up...so I set it where it seemed to be the best and that's where it had been set by the PO.
    This was wrong and the light later showed that.

    By the light.....
    I found the mark by the light it was way way advanced.
    Moving the distributor moved the mark closer to the pointer. The engine slowed and began to change tone.
    I did not realize how "tinny" it sounded until I set it on the mark.
    It went from a tinny idle with a skip to a slower deep baritone...rock steady idle.

    The light flickering at a too advanced idle....acted crazy because it was crazy....

    Timed correctly,
    The light actually seemed brighter and steady.

    Double check the simple stuff. Go by the data....Go by the timing light.

    Resolved....
    It was too far advanced.
     
    MantulaMan and waxhead like this.

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