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Thread: Vacuum Pump Bypass Setting?

  1. #1
    Senior Member MASTER BUILDER TheEngineer's Avatar
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    Sep 2007
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    Moore Oklahoma
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    129

    Vacuum Pump Bypass Setting?

    I have a stroker SBC 427 race engine with 14.7-1 Compression, wet sump and it turns 7500 RPM. I just installed a Moroso enhanced 3-Vane vacuum pump with a Moroso 22637 relief valve. Internal shims in the relief valve change the bypass settings.

    The valve has five different inch pound bypass settings; 10, 12, 14, 16 and 18. I just set it in the middle to 14 inch pounds (not knowing exactly where it should be). It is pulling about 5 inch pounds at an idle and increases with RPM.

    So, what does everyone think the bypass should be set to on this engine?

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

    Vacuum

    My choice would be 12" max.

    Too much vacuum and lubrication can be robbed from splash parts like wrist pins.

    Otherwise, what ever makes highest dyno figures or fastest ET.

  3. #3
    Senior Member RACING JUNKIE
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    May 2003
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    Coldwater, MI
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    2,998
    12-14" will be plenty at rpm.
    David Lanning
    IHRA NHRA 387B

    Fleenor Racing Transmission
    419-280-1406
    Lanning Electric
    Complete Drag Car Wiring
    APD Race Engines
    www.apdracing.com

  4. #4
    Senior Member MASTER BUILDER TheEngineer's Avatar
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    Sep 2007
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    Moore Oklahoma
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    129
    Thanks for the inputs!

    I have a race this weekend, so I'll get to see if the car picks-up some with the new vacuum pump. The car has been running fast and very consistent this season, with 1.28 60fts and 5.80s 1/8 mile ETs @ 118 MPH. Foot-braking it in the NO-E class.


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