A cam drive apparatus comprising a magnetic gear adapted to communicate rotational movement between a crankshaft and a cam shaft, wherein said magnetic gear comprises an outer member comprising a plurality of circumferentially spaced magnet means, said outer member being mounted for rotation with one of said crankshaft and camshaft, an inner member comprising a plurality of circumferentially spaced magnet means, said inner member being concentrically arranged within said outer member to define an annular gap therebetween, and an intermediate member comprising a plurality of circumferentially spaced ferromagnetic pole pieces located within said annular gap between said inner and outer members and being mounted for rotation with the other of said crankshaft and camshaft.