Holley 4BBL Vacuum Secondary 600CFM Stage 2 – 1850S2





  • Metering block design is selected based on your engine combination
  • High flow .130″ needle and seat assembly.
  • Floats are modified based on applications, drag float, single taper, double taper
  • Drill idle air bypass holes in primary throttle blades to maintain proper throttle blade angle at idle, ensuring proper function of idle and off-idle circuits.
  • Choose best metering block design to match your engine specifications, and class rules if applicable.
  • Choke tower is removed with Bridgeport vertical milling machine to increase air flow, and balance air flow of primary and secondary venturis. This promotes increased high rpm horsepower. This is a no cost option however an optional electric choke can be
  • Booster design is chosen based on your engine specifications, then balanced and modified for increased signal strength and atomization characteristics, providing crisper throttle response and drivability, as well as increased HP and TQ thru-out the rpm
  • For class rules that do not allow secondary metering blocks. We install a secondary metering plate that features; removable standard holley jets, adjustable transition circuit and increased fuel delivery.
  • Secondary Metering block installed to allow tuning and to balance the primary’s and secondary’s, fuel delivery characteristics for maximum cylinder to cylinder distribution.
  • Quick change spring kit installed to allow secondary opening rate changes (Faster for tacky tracks, slower for better traction on dry or slick tracks) in seconds.
  • Same as Stage 1 plus:
  • All circuits will be modified and tuned to match the specifications of your engine combination, Including:
  • Emulsion, High Speed Air Bleed, Idle, Idle Air Bleed, Main Well, Main Well Exit, Power Valve, Transition

Additional information

Weight 15 lbs
Dimensions 15 × 15 × 15 in


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