a variable camshaft assembly which serves to vary the timing of poppet valves in an internal combustion engine . an axially movable wormed camshaft controls a number of splitable cams of conventional cross section operating individual valves . when the camshaft is shifted axially , each valve operating cam splits into two operating elements . when the raised noses of the splitable cam elements are in alignment , the valve event is minimal . when the raised noses are in misalignment , the valve event is extended .