Abstract: An injection pump for diesel-cycle internal combustion engines includes a casing (1), a cylinder (6) within the casing and communicates, via at least one radial aperture (51), with a fuel intake chamber (3), and a piston (7) sealedly slidable within the cylinder and which, by external command, can also rotate about its axis to assume different angular orientations about a reference plane. In its jacket, a helical groove (72) opens into an axial groove (71), wherein the top, or roof, of the piston (7) is connected via a hole (77) to two channels (178, 179) provided at different levels in the piston jacket.

Abstract: A cover for a valve rocker compartment of an internal combustion engine which comprises a hollow shaped casing (9) for closing the compartment containing the rockers (6) which operate the engine intake and exhaust valves (22; 33), and a duct system which connects the shaped casing to the engine air intake manifold (2). The duct system is intercepted by a valving member (31) which is maintained in the open positiion by an elastic member of predetermined load, but closes said duct system when the vacuum in the manifold reaches an undesirable value.