The standard by which all other power valves are measured. QFT's exclusive in-house design has become the power valve of preference by professional race teams in virtually every circuit where carburetors are used. Not only does the FOUR DOOR(R) power valve have a much greater flow capacity, vital for methanol applications, but a quicker response rate and tighter limit bands allow engine builders to precisely tune the power enrichment phase of their calibration. Each FOUR DOOR(R) power valve is hand tested and set to the stamped value. The opening and closing specifications are ½ inch HG above and below the stamped value. The thicker molded diaphragm adds increased protection against backfire induced rupture. This power valve design is covered by U.S. patent # 652,048,8B1.