A valve seal for a rotary valve assembly for use in an internal combustion engine of the piston and cylinder type, the valve seal having a valve seal body member having a curved annular upper surface conforming to the spherical periphery of a spherical rotary valve, the valve seal body member having a centrally disposed aperture there through defined by an inner circular side wall, the valve seal body member further having an outer circumferential side wall having a plurality of mounting ribs for the positioning of lateral sealing rings, the valve seal body member further having a plurality of vertical axial throughbores formed between the inner circular side wall and the outer circumferential side wall for pressure equalization.