The object of this invention is to simplify the timing system of all types of internal combustion engine. The system eliminates existing conventional timing trains. The hydraulic, mechanical or electrical/electronic direct timing systems that form the subject of the invention offer minimal resistance and minimal transmission. The piston strokes are given directly by the crankshaft by means of a system fixed thereto which via a mechanical or hydraulic or electrical or electronic system transmits the strokes to the cylinder valves. The system can be connected to all types of indirect transmission and has adjusting systems that allow it to be adapted to suit all types of internal combustion engine.