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Thread: High RPM flutter and pop on Big Block Chevy In pulling truck

  1. #1

    High RPM flutter and pop on Big Block Chevy In pulling truck

    Hey guys have a 468 big block, with flat tappet Lunati cam Oval port big valve heads, wieand team G intake with 850 Dbl pump Holley Carb that has been modified, All brand new MSD ignition 6 AL box, Pro Billit Dist New coil and Taylor 409 10.4 wires, Holley Blue pump with reg, All #8 Stainless lines with AN fittings. We have a High RPM flutter and pop from 4500 to 8500 RPM, WE have changed everything except the carb and valve springs My springs are K-Motion K1000 1.625 triple springs they do have some age on them but the pressure readings are good. Im running #86 jets in primary and#90 in secondary, I have 50cc pumps on both ends and the correct nozzels and screws. Was told possibly have a lean condition and need to richen up by 2 to 4 sizes bigger on the jets. The plugs look fairly good, Possibly a little grey but not too bad. Any help would be greatly appreciated, thanx Dennis..

  2. #2
    Senior Member DYNO OPERATOR
    Join Date
    Jan 2004
    Location
    central Illinois
    Posts
    459

    high

    Put a fuel pressure gage where you can read it during a pull. You probably don't have enough fuel pump to do the job. Blue pumps are for street cars.

    Maybe a Areomotive A2000 would be better. There are some new ones listed for sale in ads. Look for the guy from Monee, Illinois. Under fuel systems.

  3. #3
    Senior Member RACING JUNKIE TheRabbit's Avatar
    Join Date
    Jan 2007
    Location
    Augusta, Ga.
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    2,295
    An 850 is no where close to what you need . On a 468 @ 7,600 you need at least 1,050min to 1,150 cfm. I wouldn't run a holley blue pump either.
    Areomotive for me.

  4. #4
    Yea I realize 850cfm is small but the rules only allow a 750 style base, no dominators.. This 850 dbl pump is measuring and flowing more than 1200cfm

  5. #5
    Senior Member RACING JUNKIE
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    Dec 2007
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    ohio
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    I would run more jet for sure. are you runing a power valve in the front, and does the carb have screw in air bleeds, and if so what size high speed bleeds?

  6. #6
    It does not have a power valve, just the plug. The air bleeds are have been drilled but are not replaceable, was told with alcohol jets it has been modified to run methanol but rules allow pump gas only. I switched the jets to 92 in pri. and94 in sec and did help it at over 5000 RPM but its still acts crazy from 2500 to 4500 while you are going through the range to get to 7500 to start leaving with the sled. when it got to 5000 it smoothed out alot better.. so i think where on the right track.. It acts like it could even stand a little more fuel its not bogging or smoking, and throttle response is really good. Thank you all so much for helping me it is nice to see some improvment. I welcome any and all suggestions..

  7. #7
    Senior Member RACING JUNKIE
    Join Date
    Dec 2007
    Location
    ohio
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    810
    If you have a pin gauge set or small drill bit's, see how large the idle air bleeds are. they also influence how rich or lean the transition slots are. but, with that being a converted meth carb, and some of the mod's sounding a little strange, imho, i would try another carb.


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