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Thread: What's your Launch RPM

  1. #1
    Senior Member MASTER BUILDER
    Join Date
    Sep 2008
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    Red Deer, AB Canada
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    213

    What's your Launch RPM

    I was wondering what your two step is set at for launch with a transbrake?
    I had mine set at 5200, but the last trip to the track, I reduced it every run by 200 RPM to 4600 and found my 60 foot times improved. Is this unusual?
    2000 pound dragster with 598 BBC and powerglide.

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

    Whats

    Every car's different. My 3000# door car likes 4600 too.

    If you run up nearer the converters stall it does not have as much torque multiplication left to help get you off the line. Lowering the RPM allows more multiplication, especially on a powerglide. It may depend if that puts the engine out of its best torque range.

    Like my ol buddy Steve Griner, used to say, " A Powerglide is a lousy transmission with only a 1.76 first gear ratio, until you couple it to an 8" 6000 RPM stall converter, then look out." (That guy knows more about the transmission game than most everybody else, I think. He was a pioneer of the transbrake, the lock up converter, and the 904 3 speeds for sbc Comp Eliminator.)

  3. #3
    Senior Member SENIOR BUILDER
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    Nov 2008
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    Phoenix AZ
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    I two step at 4800 in a 1850# small block altered, converter will do 6800 flat out. Anything over 5400 and I get into tire shake country.

  4. #4
    Senior Member RACING JUNKIE
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    David Lanning
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  5. #5
    Senior Member RACING JUNKIE TheRabbit's Avatar
    Join Date
    Jan 2007
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    Augusta, Ga.
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    2,295
    I know everybody thinks my set ups are different than the strip, but the really aren't by much. I've learned the hard way the harder you hit the suspension the harder it is to make the vehicle go forward instead of down. The one thing you do not want is to hit the tires so hard you kill the shock, lift the front end then the front fall right back down and unload the rear, then finally settle down and take off.
    Like above, every vehicle is different, becuase of weight, hp, gears, springs, shocks. and so on. Don't be scared to leave at a lower RPM. I leave between 3,600 and 4,000, sometimes even as low as 3,200. Almost always anything above 4,200 I slow down a tenth on my 60' times.

    When guys at the track ask me what I leave at I always tell 'em 5,400 :wink: .


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