Abstract: An inlet manifold 7 for both banks of cylinders of a V-configuration internal combustion engine has two different lengths of tuned inlet passage between a plenum 14 and an inlet valve 3. A first length extends from an opening 13a in one face (in this case the upper) of the plenum 14. A second length extends the first length when valve 13 closes the opening 13a, passes along passage 16 around the side of the plenum remote from the cylinder 2, and communicates with the other face (in this case the lower) via an opening 18. It is possible to construct such a manifold in three parts: a plastics moulding 10 defining the plenum 14; two metal pressings 8, 9 which engage each other; and a third metal pressing 11. Such a construction can be cheaper and lighter than hitherto.

Abstract: A part of an exhaust system 1 for an internal combustion engine has a valve 2 which can be moved by means such as a vacuum actuator 3 from a fully open inoperative position to an operative position in which it restricts the exhaust passageway by a variable amount. In the operative position, resilient means such as a coil spring 8 urges the valve to close the exhaust passageway against the pressure of exhaust gases, thereby increasing the backpressure on the engine in a controlled way. This is done on start-up to reduce the warm-up time of the engine and to reduce hydrocarbon emissions. When the engine has warmed up, the actuator 3 moves the valve to its inoperative position.

Abstract: An internal combustion engine has an integral cylinder block, crankcase and sump structure made in two halves 1, 2. The material of the halves is chosen for lightness. The pressure pulsations in the cylinders are taken by long steel bolts 14, 15 which extend from the top of the cylinder head to a bearing structure comprising yokes (steel clamping members 8, 9 clamped together by traverse fasteners 12, 13) holding together the two main crankshaft bearing housing halves 6, 7 which are formed integrally with each half of the integral engine structure. The integral halves do not have re-entrants and can be produced simply by casting, pressing or moulding.