To achieve the power mixtures needed for wide open throttle operation, the Rochester Products carburetor employs a vacuum operated power diaphragm, stem and calibrated spring located in the cover and power valve in the bowl. This system is built upon the principle that sudden acceleration is always accompanied by an immediate corresponding decrease in intake manifold vacuum. A direct vacuum passage “M” through the carburetor throttle body, outer housing, and cover to the intake manifold insures instantaneous diaphragm action to operate the power system.

Attached to the cover of the carburetor is the neoprene diaphragm, stem, and calibrated spring assembly “J”. Directly underneath the stem in the bowl is the power valve “K”, pressed into the connecting passages between the power valve and the main metering jets are the calibrated power restrictions “L”. At any manifold vacuum above 8” the diaphragm is held UP by vacuum which in turn holds the stem above the spring loaded plunger in the power valve, so that no fuel passes through this calve. Opposing this suction is the power spring surrounding the stem. This calibrated spring at any vacuum lower than 8” forces the stem down, which unseats the spring loaded plunger in the power valve, permitting fuel to pass through the power valve. This fuel is then metered by the power restrictions “L” and joins with the fuel from the main metering jets to be delivered to the engine.