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Thread: Missfire @2500 rpm

  1. #1

    Missfire @2500 rpm

    hi guys
    At 2500 t0 3000 cruse rpm i have a missfire but when i stand on
    it no miss car pulls hard . all msd new wires and cap :idea:

  2. #2
    Senior Member MASTER BUILDER
    Join Date
    Apr 2006
    Location
    Ms.
    Posts
    191
    Vacuum leak maybe???
    Unpredictable Pro Mudd Racing
    2009 MRA Pro Mod Champion
    3 time National Record Holder

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  3. #3
    Senior Member RACING JUNKIE
    Join Date
    Dec 2007
    Location
    ohio
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    810
    sound,s like vac leak, to me also.

  4. #4
    Senior Member DYNO OPERATOR
    Join Date
    Aug 2005
    Location
    Rifle Colorado
    Posts
    585
    More info on the car/engine would help. Street, race, ign type, vacuum advance, valvetrain, etc....if it has vacuum advance, try unhooking it. It may be messed up and advancing it too far at part throttle/high vacuum.

  5. #5

    Missfire @2500 rpm

    hi
    It is a street MSD DIS........with no vacuum davance
    zz4 350 /355 power plus intake open plain crane hyd roller cam
    234/243@50....539/558 lift...adv dur 398.304 crane 1.5 roller rockers
    demon 750 carb.......after 2500rpm......car runs strong

  6. #6
    Senior Member RACING JUNKIE
    Join Date
    May 2006
    Posts
    2,044
    You changed the cam correct?
    More lift and duration than the crate motor cam had?
    I think its fuel related.
    Sounds like the power valve is trying to open up part throttle and dumping unatomized fuel down into the intake or drippling out of the boosters. With the car in park have someone rev it up to around 2500 and CAREFULLY lean over the carb and see if fuel is drippling out of the boosters.
    If my memory serves me well, you need a power valve with a lower number with a higher lift cam or just take it out put a plug in it then go up about 4 jet sizes and be done.
    Goodluck, Charles
    ***IN GOD WE TRUST***


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