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Thread: Running A 671Blower On A Eng. That Already Has 12.5:1 compre

  1. #1
    Senior Member MASTER BUILDER
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    Running A 671Blower On A Eng. That Already Has 12.5:1 compre

    My de-stroked 400 chevy w/ domes. What pulley set-up should I run w/ 12.5:1 compression. Was going to slow the blower down guite a bit, just not sure which pulley to use. This engine is an alky injected eng. currently. The car is a Front Engine Dragster. This is a street blower kit. Wieand is only helpful on strock. Any suggestions. Kris

  2. #2
    Administrator RACING JUNKIE bjuice's Avatar
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    8mm or 13.9/14mm drive pulleys ?

    also IMO you are on the high side of the static compression .i think i would ask myself how much final compression would i want to make then back into the pulleys..after you figure this i can give you some pulley ratio's etc...

    here is a formula to determine final compression ratios from BDS

    Final compression Ratio (FCR)=[(boost /14.7)+1]xCR
    Boost = Max blower boost
    14.7= psi @ sea level
    CR= engine compression ratio
    Bjuice..

    "I'M YOUR HUCKLEBERRY ! "

  3. #3
    Senior Member MASTER BUILDER
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    671 blower

    Bjuice, I have a wieand setup w/ 1/2"pitch, just a street blower. Not trying to compete just doing the nostalgia shows every now and then. But when I go I got to go. Have 39,35,32,38,33tooth pulleys. Normally I run the right piston for the application. Though I do hear of some folks running high static and just just taking (ALOT) of speed out of the blower.

  4. #4
    Administrator RACING JUNKIE bjuice's Avatar
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    Re: 671 blower

    Quote Originally Posted by kbartley
    Bjuice, I have a wieand setup w/ 1/2"pitch, just a street blower. Not trying to compete just doing the nostalgia shows every now and then. But when I go I got to go. Have 39,35,32,38,33tooth pulleys. Normally I run the right piston for the application. Though I do hear of some folks running high static and just just taking (ALOT) of speed out of the blower.
    Bottom upper
    39 38 2.7 overdriven
    39 33 18.2 overdriven
    39 32 21.9 overdriven
    39 35 11.4 overdriven


    32 39 20.5 underdriven

    if you want anymore combo's let me know which ones and i will post it.

    Brian
    Bjuice..

    "I'M YOUR HUCKLEBERRY ! "

  5. #5
    Senior Member RACING JUNKIE
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    haha.. im sure your runnin 8mm and a 1440 belt? 52ish on top and 44-48 on bottom or in that ball park. you could probably run it close to 1to1 since its alky injected but we will see for how long? Be carefull that it doesnt rip the front of the crank off.


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