Annular boosters on a Tunnel Ram

More about annular boosters:

The Holley Main System is made up of two major components:
The Annular Discharge Booster Assembly (talking about modern Carb Design stuff vs the old "Straight Leg Boosters" in this post) and the Main Air Well System.

The Annular Discharge Booster Design induces higher air velocities at the point of the discharge which results in increased signal strength to the Main System. The configuration of booster and the size of the booster assembly was established by running signal strength measurements fuel flow curves, and fuel discharge profiles on Holley Engineering's Wet Flow Benches in Warren Michigan.

The total airflow of the carbs was reduced slightly, the target was to have no reduction of airflow. Most Annular Discharge Designs will flow approximately 5 cfm less per booster position so on a 850 cfm carb with the annular boosters the air flow would be 830 cfm.

The Main Well operation is the same as the Idle System.

The High Speed Air Bleed meters the "bleed air" to the Main Well. The "bleed air" is fed thru holes in the metering block (emulsion holes) and form a homogeneous fuel/air mixture that is then discharged thru the Annular Booster assembly.

Obviously the High Speed Air Bleed is a "calibration item". The Main Fuel Jet is the "calibration orifice" for the fuel from the fuel bowl.
The High Speed Air Bleed is determined based on the range of Main Jets determined by the Calibration Strategy and Engine Dynamometer data.

The Idle Jet (Idle Feed Restriction) is determined by the approximate fuel required to power the engine in the Idle and off-idle speed ranges.

The diameter of the Bleed Holes (emulsion holes) and number and position of those holes have a direct effect on the vehicle "drive characteristics"
The Top Hole(s) affect crowd and part throttle acceleration response. The Bottom Hole(s) are used to initiate and accelerate the Main circuit fuel and air flow thru the booster.

NOTE: Changes made to the Air Bleeds, for fuel curve contouring, DO NOT REQUIRE changes in the emulsion holes

A change in the Main Jets will require a potential change in the air bleed holes at times. This is a calibration tuning effect.

If the proper balance between the Main Jets and the Air Bleeds is not maintained, a depreciation in vehicle driveability will result.
The Fuel/Air System of a Holley carburetor may be classified as a tuned circuit carburetor and will be extremely stable and responsive to engine mode changes if proper methods of tuning are observed. A Air/Fuel meter is recommended.

Tom V.