Abstract: A cylinder head (10) for an internal combustion engine, having at least two inlet valves (20) associated with the or each combustion chamber, the inlet valves (20) being supported in the cylinder head (10) with their axes spaced from one another in a first direction, at least two exhaust valves (22) with their axes of reciprocation also spaced from one another in the first direction and at least two receiving formations for operating elements (such as a spark plug (38) and fuel injector (40)), the receiving formations opening into the combustion chamber portion in a central region bounded by the heads of the valves, wherein the receiving formations are inclined to one another so as to diverge generally in the first direction as they extend away from the combustion chamber portion.

Abstract: A valve spring mechanism is provided which is suitable for use with the inlet or exhaust valves of an internal combustion engine, and includes a valve head and a valve stem. The mechanism includes a piston/cylinder arrangement in which the cylinder surrounds a portion of the valve stem to define a chamber. The piston is slidable and sealingly mounted on the valve stem. The mechanism also has force transmitting means for transmitting the force produced on the piston by gas pressure within the chamber to the valve stem, and a spring operating on the piston and the stem of the valve for applying a force to the stem tending to close the valve in the event of failure of chamber gas pressure. The spring is positioned to maintain it in a compressed condition during normal operation of the mechanism as a result of gas pressure within the chamber.