Why does my Carter AFB backfire?

Discussion in 'Carter' started by CanadianBird, Dec 31, 2005.

  1. CanadianBird

    CanadianBird Silver Level contributor

    I have 9000 series carter AFB competition carb on my 300 CI 4 bbl buick. It is a 500 CFM, with 086 on primaries and 095 on secondaries. When accelarting abruptly I am getting a bog and a backfire with flame coming up through what I think was the secondaries. This carb has no more than 20,000 miles on it and I put a full rebuild kit in it today, it was dirty as the car sat for 4 to 5 years with the odd firing up, the carb had some sediment and a bit of corrosion but no carbon and barly no varish build up...it was doing this before I put the kit in it...any suggestion? I was told that this car only had 47,000 miles on it...based on he condition of the car, both bodyshop and myself felt that this was pretty accurate...any suggetions or thoughts would be appreciated.
     
  2. Smartin

    Smartin antiqueautomotiveservice.com Staff Member

    Check the timing yet?
     
  3. CanadianBird

    CanadianBird Silver Level contributor

    I should have seen that coming. No I have not, Shame on me. I will and will post back later. Thanks. Happy New Year!
     
  4. flynbuick

    flynbuick Guest

    An air leak under the manifold gasket for one.
     
  5. Smartin

    Smartin antiqueautomotiveservice.com Staff Member

    A malfunctioning secondary air flap will also cause this. I don't think the Carters have the flaps like the Qjets do, though.

    Does it run well, otherwise?
     
  6. CanadianBird

    CanadianBird Silver Level contributor

    We I have not really had out a lot, starts in a blink, good idle, a nice gentle acceleration seems fine but if you step into it....blah...POW! and will at times kill engine.
     
  7. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Vaccum leak. Sounds like it is going lean, backfire through the carb. The Carters have a counterweighted secondary air valve. Make sure it isn't stuck open.
     
  8. wkillgs

    wkillgs Gold Level Contributor

    I was thinking it's a lean condition as well....
    Could be a defective accelerator pump.
    Easy to check....with the engine off, look into the carb, and pull the throttle lever...you should see a strong squirt of fuel.
     
  9. CanadianBird

    CanadianBird Silver Level contributor

    Accelerator pumped replaced...will check for visual squirt...I will check timing then consider following options...

    Accelerator pump has 3 diff positions, change to see if any diff.

    Add some weight to the secondary weights to delay secondaries till higher RPM achieved...

    Smaller metering jets on on secondaries...

    Thoughts anyone? :Do No:
     
  10. Smartin

    Smartin antiqueautomotiveservice.com Staff Member

    Check to see that the secondary flaps are not stuck open all the time.
     
  11. CanadianBird

    CanadianBird Silver Level contributor

    I will check it out Martin, Thanks.
     
  12. CanadianBird

    CanadianBird Silver Level contributor

    Thought I would bring some closure to this. Borrowed a timming light. Read up on ignition system :Do No: (that stuff IS rocket science)...cannot get the fancy SNAP ON timming light to work! :Dou:

    May as well check my RPM at idle and make sure that my two screws at front of carb are set at MAX RPM...they were not...i adjusted...Oh and I was patient and made sure my engine was warmed up...pulled out the garage, stopped at street, floored it and BAM :3gears: those rear wheels keep spinning till you let of the gas!!!! I am so pleased! :TU:

    Have a gleat weekend!

    :beer
     

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