Carburetor back fire

Discussion in 'Troubleshooting & Diagnosis' started by Justin79maro, Apr 10, 2017.

  1. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

    8,806
    130
    Nov 4, 2004
    Ringgold, GA
    Sounding more like an intake valve issue, not closing all the way or not seating properly. You might want to rent a bore scope and start looking. I bought one a couple years ago when I dropped a nut in the intake, not very expensive at all.

    Don't remember, but have you done a leak down test?
     
  2. Justin79maro

    Justin79maro Member

    88
    1
    Jan 15, 2015
    Bonne terre, missouri
    Yep working just fine. I even pulled it apart to check it while changing power valves
     
  3. APEowner

    APEowner Veteran Member

    636
    10
    Dec 9, 2013
    Albuquerque, NM
    What are you running for an ignition system? Had the timing moved when you first checked it?
     
  4. Justin79maro

    Justin79maro Member

    88
    1
    Jan 15, 2015
    Bonne terre, missouri
    No I haven't
     
  5. Justin79maro

    Justin79maro Member

    88
    1
    Jan 15, 2015
    Bonne terre, missouri
    Gn hei dizzy cap and a msd 6al
     
  6. Justin79maro

    Justin79maro Member

    88
    1
    Jan 15, 2015
    Bonne terre, missouri
    Just did a compression test in the driver side and it was about 90 and all the plugs were black.
     
  7. cadillac_al

    cadillac_al Veteran Member

    512
    33
    Apr 22, 2015
    Maine
    All cylinders on drivers side are 90 or just one? It does sound like an intake valve like Corky said. Since it happened after track day, maybe floated them and bent one
     
  8. Bandit723

    Bandit723 Veteran Member

    2,251
    262
    Oct 1, 2016
    Waupaca WI
    Do you have a vacuum gauge on this thing? Might help validate the bent/sticky valve. You would be seeing erratic vacuum readings.
     
  9. Justin79maro

    Justin79maro Member

    88
    1
    Jan 15, 2015
    Bonne terre, missouri
    They all showed 90-100 except one showed 0 and number 6 & 8 I couldn't get the tester in
     
  10. Bandit723

    Bandit723 Veteran Member

    2,251
    262
    Oct 1, 2016
    Waupaca WI
    so number one is the one that was not firing when you tried the timing light?
     

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