F01L 1/34406

Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of means for changing the timing of the valves without changing the duration of opening {and without affecting the magnitude of the valve lift} changing the angular relationship between crankshaft and camshaft, e.g. using helicoidal gear {using helically teethed sleeve or gear moving axially between crankshaft and camshaft the helically teethed sleeve being located in the camshaft driving pulley}