Abstract: In a valve assembly for a pressurized fluid dispensing container, such as those commonly known as aerosol cans, the filling with propellant gas at the very high speed and pressure needed to meet current production rates presents problems. The invention involves crimping the center boss of the sheet metal mounting cup in such a way, and at a point below the enlarged head portion of the valve housing, that the part of the boss above the crimp and around the valve housing bows outwards to provide clearance for "gassing". There are notches in the lower part of the outside of the head portion but these stop short of the upper face of the head. The valve stem may also have external axial grooves placed to increase the effective cross-sectional area during gassing.