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Oddfire Backfire

Discussion in 'Flat Fender Tech' started by Kolten, Mar 27, 2020.

  1. Mar 27, 2020
    Kolten

    Kolten New Member

    Duvall, Washington
    Joined:
    May 9, 2016
    Messages:
    29
    So as some of you are aware I solved a timing issue with my CJ2A - Buick 225 V6 where one engine bank was hot while the other was cold. We resolved this with a new HEI distributor and retiming it. I hadn't started the jeep in a few days and I noticed some crap in the fuel filter (rust), so I decided it was finally time to replace the tank. I got the new tank in added and when I was putting the fuel filter back on noticed the carburetor was loose. I tightened it up and started the jeep. It runs alright but when I max out the throttle quickly and then let off I will get two backfires off the drivers side exhaust. Not during the acceleration but only after I quickly release the throttle. Would this be caused by an vacuum leak since the carburetor was loose? I mean other than the backfire on the deceleration everything seems to run ok.
     
    Kolten, Mar 27, 2020
    #1
  2. Mar 27, 2020
    47v6

    47v6 junk wrecker! 2023 Sponsor 2022 Sponsor

    USA
    Joined:
    Oct 25, 2006
    Messages:
    5,801
    unburnt fuel with free flow exhaust?

    Use a vacuum gauge to set up your carb and HEI.
     
    47v6, Mar 27, 2020
    #2
    ITLKSEZ likes this.
  3. Mar 27, 2020
    ITLKSEZ

    ITLKSEZ Hope for the best, prepare for the worst

    Spokane Valley, WA
    Joined:
    Aug 13, 2015
    Messages:
    6,683
    Make sure all your manifold/header bolts are tight, and there are no cracks or rust-throughs close to the head on that side.
     
    ITLKSEZ, Mar 27, 2020
    #3
  4. Mar 27, 2020
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
    Joined:
    Jul 18, 2013
    Messages:
    5,646
    I would start with exhaust manifold leak as well - or possibly exhaust leak/crack in header pipe.

    Not that it is really the issue, but sometimes helps manage rapid throttle deceleration - there is a dashpot on the throttle (at the carb) that helps minimize how fast the throttle closes down, and helps minimize unburnt fuel going out the exhaust (and potentially backfiring).
     
    FinoCJ, Mar 27, 2020
    #4
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