Abstract: An aluminium or aluminium alloy cast piston has a piston ring carrier of a ferrous material encast therein. The carrier has sides which converge towards their radially inner ends. As a result of this, and as a result of a lesser coefficient of thermal expansion of the ferrous material of the carrier as compared with the aluminium or aluminium alloy of the piston body, solidification of the piston material causes elastic outward expansion of the carrier which is sufficient to prevent any clearance occurring between the two parts, even at operating temperatures. Thus the carrier is not, and need not, be locked to the piston body against radial movement.

Abstract: The manufacture of piston rings for internal combustion engines comprises making a ring blank of which the diameter over the outer periphery is greater, and the diameter within the inner periphery is less than that required in the finished ring. A gap is cut in the ring blank to afford two free ends and the ring blank is held in a closed position by the application of a force only to each of the free ends of the ring blank. One or more ring blanks are then clamped in a closed position and machined so that the inner and outer peripheries are circular. This enables a ring to be produced which conforms very closely to a required shape and which thus, in use, provides a good seal between a piston and the associated cylinder of an internal combustion engine.