Abstract: Apparatus for adjusting the timing of a valve, particularly but not exclusively for use with a four-stroke internal combustion engine. The apparatus includes a cam, which engages a cam follower which is arranged to actuate a valve mechanism in response to rotation of the cam. The cam follower is moveable in translation relative to the axis of rotation of the cam to vary the extent of actuation of the valve in response to rotation of the cam. The cam follower is shaped so that for a part of a cycle of rotation of the cam, the line of action of the force from the cam to the follower forces the follower to move in translation. This movement is greater at low cam rotational speeds than at high cam rotational speeds and, due to the profile of the surfaces of the follower, the translational movement provides varying extents of valve actuation in dependence upon cam rotational speeds.

Abstract: A structural unit for an internal combustion engine, including an engine region (for instance, a part of a cylinder head directly exposed to the cylinder firing zone) that requires direct cooling in use. Instead of applying the cooling to the region itself, it is applied to a separate structure with a connection to the region, the section of the connection corresponding in shape with that of the region itself. Both gaseous and liquid cooling of the structure are described.

Abstract: An internal combustion engine cooled by the forced passage of fluid through ducts, in which such ducts are confined to the individual regions of the engine liable to overheat, the remaining parts of the engine which in operation rise only to acceptable temperatures being left free from such ducts. The invention includes structures to resist separation of the engine components under firing loads and to improve rigidity.