Abstract: An internal combustion engine has an inlet port side angle (B) which is greater than 60° and is preferably 101°±3°. The exhaust valve side angle (C) is preferably 93°±3°. The inlet valve seat (3) is located closer to the longitudinal axis (8) of the cylinder than the exhaust valve seat (4) and the imaginary line (16) which passes through the geometric centres of the valve seats (3, 4) is offset from the diameter (7) of the cylinder. This combination of characteristics gives an engine having a high specific power output, low specific fuel consumption, low emissions of carbon monoxide and unburnt hydrocarbons and a cool exhaust gas containing a significant volume of oxygen.

Abstract: A fluid pump includes a fluid-tight housing containing two spaced, externally-toothed pulley wheels, an internally-toothed drive belt that wraps around and engages the teeth of the two pulley wheels and moves as they rotate, and a guide block in the space between the two pulley wheels. The housing includes a fluid outlet port adjacent where the drive belt engages a first of the two pulley wheels to discharge fluid pressed out from between the teeth of the drive belt, and a fluid inlet port adjacent where the drive belt disengages from the first pulley wheel. The guide block defines a first face that extends with the drive belt to a nip where the drive belt engages the first pulley wheel and a second face that includes a first portion which extends from the first face in an arc around the periphery of the first pulley wheel and a second portion which extends away from the periphery.