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Thread: need help

  1. #1
    Senior Member RACING JUNKIE
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    need help

    ok guys i need some help on trying to find out why my carb has just developed a dead spot in it. the only thing i changed on the motor was intake and locked the msd dizzy out. if you floor it there is no hesitation. but if you just ease into like just pulling out on the street it has a dead spot. it doesnt want to idle just right either. its a 1050 HP dominator. it never done this until we changed the intake and locked out the dizzy. thanks for any help

  2. #2
    Senior Member DYNO OPERATOR
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    My guess would be a vacuum leak caused by misalignment of the intake or gasket. You might try unlocking the distributor before you pull the intake though. You did reset the timing after you locked the distributor, right?
    Johnny

  3. #3
    Senior Member RACING JUNKIE curtisreed's Avatar
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    I don't think the locked distributor is the cause. With the engine off slowly open the throttle and watch to see if you lose accelerator shot. Could possibly need an idle bleed change, checking for vacuum leak is not a bad idea though. jmarkaudio (Mark Whitener) on here is pretty good with dominators.

    Curtis

  4. #4
    Senior Member DYNO OPERATOR
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    I don't think the locked dist is the problem either unless the timing wasn't set, but since 2 things were changed, it would be easy to eliminate that one....could be pump shot though. The pump arm should move as soon as the throttle does. I've seen some people set the arm with clearance because of a misinterpretation of Holley's instructions on arm adjustment.
    Johnny

  5. #5
    Senior Member RACING JUNKIE
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    Sounds like too much timing at low rpms, what is it locked at 38 degrees? what is the compression on the engine? If your driving it on the street it may also want to run warmer

  6. #6
    Senior Member RACING JUNKIE jmarksdragster's Avatar
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    The other guys have posted some good things, you made changes and now have issues. If the carb worked well before, I would be looking first for a vacuum leak. What are the engine specs? What curve did it have in it before? Few things to look at with the carb after you eliminate the others, with the idle speed set right pull the carb and make sure you have about .020 transition slot exposed in all 4. insufficient amount can cause a slight stumble. Obviously no slack in the accelerator pump adjustment at idle. And if all else is well, try going out 1/4 turn on the mixture screws. And if the carb set for an extended time while making changes you may have had some gaskets dry out, something plugged...
    Mark Whitener
    http://racingfuelsystems.myfunforum.org
    __________

    Good work isn't cheap, and cheap work can't be good.

  7. #7
    Senior Member RACING JUNKIE
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    I highly susepct a vacuum leak especially since you mentioned that it is having difficulty idling now.
    Spray some carb clean around the base of the carb, intake flanges, fogger fittings etc.

    Cp
    ***IN GOD WE TRUST***

  8. #8
    Senior Member RACING JUNKIE
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    I know this one is kinda unlikely, but I have had similar behavior from a partially plugged needle/seat due to part of some gasket material getting caught up in the needle... it was very small (probably 2-3mm). Idle was inconsistent/crap & I had a hesitation too. Scoot
    "I would walk through hell on Sunday before I fear the enemy"


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