Boost/Vacuum reference port question
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Boost/Vacuum reference port question

  1. #1
    21' Daytona DaytonaTunnel's Avatar
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    Default Boost/Vacuum reference port question

    Can someone explain these ? I'm upgrading my mech fuel pump to a Clay Smith which requires a regulator (my old Holley did not). Do I need a regulator with a boost/vacuum port ? Why ? Can't I just set the F/P at 9lbs. and go ? Thanks !!!

    P.S. Blown BBF running +9 lbs. on 92 pump.

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    Cantard 71hallett's Avatar
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    Blow through carbs need reference, draw through do not.
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster

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    21' Daytona DaytonaTunnel's Avatar
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    Quote Originally Posted by 71hallett View Post
    Blow through carbs need reference, draw through do not.
    I have boost referenced carbs now, so I don't need the boost/vacuum regulator ? Even if I don't I'd like to understand how/why that type of reg works.

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    21 Daytona Outlaw's Avatar
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    blow thru require the fuel pressure to increase 1 to 1 with boost
    pressure to maintain the base fuel pressure.

    if you did not increase it and started with 5psi fuel pressure
    and added 5 psi boost pressure your needle and seat would see
    0 fuel pressure, because of the added internal pressure
    from boost. IMO

  7. #5
    21' Daytona DaytonaTunnel's Avatar
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    Quote Originally Posted by Outlaw View Post
    blow thru require the fuel pressure to increase 1 to 1 with boost
    pressure to maintain the base fuel pressure.

    if you did not increase it and started with 5psi fuel pressure
    and added 5 psi boost pressure your needle and seat would see
    0 fuel pressure, because of the added internal pressure
    from boost. IMO
    That makes sense, thanks !!!

  8. #6
    Cantard 71hallett's Avatar
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    Quote Originally Posted by DaytonaTunnel View Post
    That makes sense, thanks !!!
    You can use a reg with the boost ref port you just leave it empty if that helps.
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster

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