An internal-combustion engine has a cylinder head, in which two shafts are mounted rotating. A first shaft is a camshaft, equipped both with cams that control the intake valves by means of an electronically controlled hydraulic device and with cams that control the exhaust valves mechanically. The second shaft is without cams and has an end coming out of the engine and constituting a power take-off for control of auxiliary service devices. The engine can be obtained with simple operations starting from an engine of a conventional type.