The power fuel system supplies fuel to the engine in the speed ranges beyond idle and slow speed. As engine speed is increased, the air flow through the venturi (17) is increased. The increased air flow creates a vacuum at the nozzle tip (14). The pressure then is lower at the nozzle than it is in the fuel bowl chamber (9) and the accelerating well (16). Fuel, therefore, flows from the fuel bowl, through the main adjustment needle and seat assembly (19) and out the nozzle (14) and into the air stream at the venturi. At the same time, the fuel in the accelerating well is forced through the nozzle air bleeds (15) in the nozzle. However, due to the size of the power jet and the restriction at the main adjustment needle seat, the fuel in the accelerating well is soon exhausted, and air enters the accelerating well through the nozzle air vent (20). The amount of air that can enter is limited by the size of the nozzle air vent. This air helps to atomize the fuel passing through the nozzle, and it helps to regulate the rate of discharge of the fuel fed from the accelerating well during acceleration. It also provides the correct mixture proportions for full throttle operation. When the throttle plate is opened suddenly to the wide open position, the fuel in the accelerating well is forced out through the nozzle air bleeds very rapidly, providing the extra rich mixture the engine needs to meet the sudden load. When the throttle is enclosed again, fuel fills the accelerating well, ready for the next acceleration.