SHASHED BOWL VENT

Discussion in 'The Venerable Q-Jet' started by shiftbyear, May 24, 2017.

  1. shiftbyear

    shiftbyear Well-Known Member

    Does anyone know why some qjets have a slashed bowl vent? Does it make any difference at all? Thanks
     
  2. carmantx

    carmantx Never Surrender

    They were on big block Buicks from 69 to 74 and some early Pontiac Quadrajets. I haven't seen them on any other units.
    I am not sure of any difference it may have provided or any reason for the engineering on it. I haven't found any documentation that discusses it. There were many design changes and differences early on in the different makes for Quadrajets.
     
  3. Cliff R

    Cliff R Well-Known Member

    Some factory "high performance" Quadrajets used a slashed bowl vent, others did not.

    All Marine units will use one, and it will be backwards so any flooding out the vent directs the fuel into the carb to help reduce the potential of an engine room fire.

    There is absolutely no benefit whatsoever using a slashed bowl vent from a performance standpoint. I've dyno'd and drag strip tested Q-jets with standard vents and slashed ones and no measurable difference either way. Hope that helps some......Cliff
     
  4. lemmy-67

    lemmy-67 Platinum Level Contributor

    The angled cut on the bowl vent helps minimize the low pressure created from airflow cutting across the opening & lowering the chance of fuel getting sucked out of the bowl. Cutting the bowl vent tube increases the overall surface area of the opening...hence less vacuum effect from the intake air flow. As Cliff said...it doesn't affect performance, just helps to keep the bowl pressure equalized & lower the chance of fuel spills.
     
  5. Cliff R

    Cliff R Well-Known Member

    Quadrajets also have other areas in the airhorn to "vent", depending on what type of Q-jet you are working with. They all vent where the secondary metering rods go thru the gasket, and there is a hole or slot (depending on what model) behind the choke flap that is open to the fuel bowl. Many also vent above the secondary POE wells. So it's pretty unlikely a q-jet will not have enough surface area for venting no matter what application and power level.......Cliff
     

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