This invention relates generally to a breather valve assembly for use in an engine cylinder head. In one embodiment, a system includes, but is not limited to, a cylinder head including at least: a rocker arm chamber including at least a breather housing mount and an air discharge port; and a valve cover positionable over the rocker arm chamber, the valve cover including at least a vent tube recess; and a breather valve assembly including at least: a housing including at least: an open bottom configured to seat on the breather housing mount such that a bottom surface portion of the rocker arm chamber forms a base of the housing; an oil/air inlet disposed near a top of the housing offset to one side; an oil outlet disposed near a bottom of the housing; a valve positioned over the oil outlet that is operable to close during a high pressure cycle within the rocker arm chamber and open during a low pressure cycle within the rocker arm chamber; an air outlet disposed on a top of the housing; and a vent tube extending between the air outlet and the air discharge port and configured to rest within the vent tube recess, wherein the breather valve assembly is squeezed in position between the bottom surface portion of the rocker arm chamber and the vent tube recess of the valve cover, and wherein the breather valve assembly is configured to relieve pressure build-up within the cylinder head by externally venting air from an air/oil mixture separated via vortex action induced during high pressure cycles while releasing separated oil back to the cylinder head during low pressure cycles.