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Technical 36 Ford flathead backfiring through exhaust WHY??

Discussion in 'Traditional Hot Rods' started by MikeO, Jan 8, 2012.

  1. MikeO
    Joined: Mar 1, 2004
    Posts: 606

    MikeO
    Member
    from MI

    new coil 12volt , carb rebuilt, new wires, valves not sticking,new points and condencer, It had thas problem before all the work and still does it any ideas??
     
  2. 29pu
    Joined: Oct 31, 2008
    Posts: 159

    29pu
    Member

    Maybe an exhaust leak at the manifold.
     
  3. could be as simple as crossed plug wires
     
  4. Slick Willy
    Joined: Aug 3, 2008
    Posts: 3,053

    Slick Willy
    Member

    Slop in the rotor shaft. Oh and what they said^^
     

  5. F&J
    Joined: Apr 5, 2007
    Posts: 13,222

    F&J
    Member

    Put up more symtoms, like when does it backfire...under a load or just sitting there, etc.
     
  6. Should be able to find the culprit by doing a compression test, a leak down test, and take a vacuum reading. My experience tells me you probably have one of the following problems, a burnt valve, or a broken valve spring.
     
    Last edited: Jan 9, 2012
  7. George/Maine
    Joined: Jan 6, 2011
    Posts: 949

    George/Maine
    Member

    If you could check the plugs and see how burning,I would guess its the middle exhaust seeing it uses same port.Any unburned gas could fire next cylinder to it.
     
  8. ronnieroadster
    Joined: Sep 9, 2004
    Posts: 1,069

    ronnieroadster
    Member

    Check the firing order its possible it was wrong befreo replacing the wires and continues to be wrong with the new wires. Flathead Ford firing order is 15486372. Cylinders are numbered as follows front to rear Pass side is 1 2 3 4 driver side 5 6 7 8.
     
  9. MikeO
    Joined: Mar 1, 2004
    Posts: 606

    MikeO
    Member
    from MI

    Thanks Guys we went through everything and it turned out the new coil was junk too ,put another one on it and it runs great :)
     

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