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Thread: Another Stumble Guestion.

  1. #1
    Senior Member MASTER BUILDER
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    Another Stumble Guestion.

    I Know you guys hear a lot of these stumble Question. So I'm gonna make this short and sweet. I Bought a new Holley Ultra HP 950 from 2500rpm foot brake start it will stumble just enough to take me down from 6.20 to 6.40 It come out of the stumble quick but it should not stumble at all. now if I take it to 3000 it want stumble. now I know I could come out everytime High RPM and by pass the stumble but I really would like to know what is causing it. there is one thing I noticed is that the rear high speed air bleed was dark brownish color and all the others look new. I Don't know about carbs so some help would be Grateful. 2670# 85 camaro 434 665 H/P- 1.76 PG - 32 X14''slicks Well it was not that short Sorry.
    Andy

  2. #2
    Senior Member RACING JUNKIE
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    Andy usually a hesitation or stumble is a lean problem. Especially since yours goes away at 3000rpm launch. First thing I'd try is turning the idle screw out a 1/2 turn or so, if its still there try a bigger squirter. Take carb cleaner and spray your air bleeds, they have little holes and tend to get plugged easily. The dye in racing fuel will gum them up also. Let me know what you find.

  3. #3
    Senior Member MASTER BUILDER
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    Thank you dParker. I will try them both. another quick question. if you run 80 jets in the spring and fall when the temps are in the high 70s what would you run in the heat of the summer @ 98 degrees.
    Thank you Andy

  4. #4
    Senior Member RACING JUNKIE
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    That a very vague question. There are many scenarios to that question. A rough answer IMO would be 2 to 4 jet sizes. Your ajusted altitude changes with temp, humidity, and baro pressure. In my experiences, there is 1 1/2 jet size change for every 2000ft of air change. Make a pass with the 80s and try 78s and see what your MPH does. If it goes up stay with the 78s.. If I didn't have a air monitor and EGT. Use your MPH, I would keep leaning my jets until I got to the fastest MPH and then go up 2 jet sizes. Usually is pretty close.

  5. #5
    Senior Member RACING JUNKIE jmarksdragster's Avatar
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    Is your timing locked? At your HP level you need ti lock the timing, no curve.
    Mark Whitener
    http://racingfuelsystems.myfunforum.org
    __________

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

  6. #6
    Senior Member MASTER BUILDER
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    Yes sir the timing is locked. Thanks for the reply.
    dParker we are in Houston so we're way down close to sea level maybe 300' above. Thanks for the advice. yall are a lot of help.
    Andy


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