The two-step power system provides better fuel distribution at the top end of the cruising range where slight enrichment is normally required. It performs this function by the use of a new type power valve assembly. Looking at the illustration, note that the power ball slightly off of its seat, (as it will normally be at the upper end of the vehicles cruising speed), the clearance between the ball and the power valve well is very little and actually controls and meters the power fuel flow. However, at wide open throttle, when full enrichment is required, the ball is moved out and past the restricted well area, at which time the regular power restrictions, pressed into the well support assembly, controls the power fuel requirements. This power valve assembly uses a barrel shaped spring to provide clearance for the spring within the lower well.