Abstract: An internal combustion engine comprises a cylinder block, an upper crankcase, and a lower crankcase, which comprises an inner casing including an outer wall and the lower main bearing housings, and an outer casing, with a space therebetween. The outer casing has a sump mounted on it. Oil drainage passages from the cylinder head face of the cylinder block extend down to meet a pair of longitudinal passages from which oil drainage ports open into the space between the inner and outer casings. These passages add significantly to the stiffness of the engine.

Abstract: An internal combustion engine inlet manifold comprises upper and lower castings which together define a plenum and a vacuum reservoir separated by a common dividing wall. Inlet tracts connect the plenum to an engine to be supplied with air and an inlet port connects the plenum to atmosphere through a variable throttle. The reservoir includes an outlet port for connection of the reservoir to a device requiring a source of vacuum and is connected to the plenum by means of a one way flow valve operable to permit the egress of air from the reservoir when the pressure in the plenum is lower than that subsisting in the reservoir but to prevent the flow of air from the plenum to the reservoir when the pressure in the plenum is higher than that subsisting in the reservoir.