Abstract: An intake system for an internal combustion engine includes first and second intake valve bores provided to face a combustion chamber and to be independently opened and closed by first and second intake valves, and first and second intake ports which are connected to the corresponding intake valve bores with a partition wall interposed therebetween and which communicate with a common intake passage. In a particular operation range of the engine, an imbalance is produced in the concentration of the air-fuel mixture flowing through the first and second intake valve bores into the combustion chamber on the basis of a difference between the amounts of fresh air flowing into the first and second intake ports. The intake system further includes a communication hole provided in the partition wall for putting the first and second intake ports into communication with each other. This provides for improvements in the lean combustibility and in the nature of the exhaust gas.

Abstract: A power unit mounting structure in a motor vehicle includes a power unit comprising an engine having a crankshaft, a transmission coupled to the crankshaft of the engine, and a differential interposed between drive axles connected to a pair of laterally spaced front road wheels of the motor vehicle and the transmission. The power unit is mounted in a front portion of the motor vehicle with its center of gravity positioned rearwardly of the drive axles extending from the differential toward front road wheels serving as the drive road wheels. A steering gearbox extends parallel to the drive axles and is disposed forwardly of the drive axles.

Abstract: A control system for a variable valve actuating mechanism for an internal combustion engine for varying the lift or timing of intake or exhaust valves in response to engine operating conditions. The control system includes sensors for detecting the pressure in the combustion cylinder and the temperture at the mounting seat of the spark plug. A warning device and fail safe conditions can be activated when an abnormal condition is detected by one of the sensors.

Abstract: A valve operating mechanism for an internal combustion engine wherein a plurality of rotatable cams have different cam profiles for operating an intake or exhaust valve differently in high and low speed ranges of the engine. A plurality of rocker arms are selectively connected or disconnected for transmitting the appropriate cam lift to the valve depending on the engine speed range. The cam profiles have dampening areas at the start of opening and the finish of closing of the valve. The dampening areas of the high speed cam have a smaller rate of change than the dampening areas of the low speed cam to minimize the possibility of engagement by a rocker arm with a cam for one speed while the engine is operating at another speed by another cam and rocker arm.

Abstract: A valve operating mechanism for operating a plurality of valves of a particular cylinder of an internal combustion engine includes a camshaft rotatable in synchronism with rotation of the internal combustion engine and having at least one cam. At least one of a plurality of cam followers slidably engages the cam for selectively operating the valves according to a cam profile of the cam. The cam followers are selectively interconnected and disconnected to operate the valves in different speed ranges of the internal combustion engine, the speed ranges including a range in which all of the valves remain inoperative. The camshaft has one or two annular raised portions in addition to the cam, and the cam followers include one or two cam followers which slidably engage the raised portion or portions. The valves remain inoperative by the annular portion or portions and are operated in a high-speed range by the cam, or selectively in low- and high-speed ranges by low- and high-speed ranges.

Abstract: A valve operating mechanism for operating a single valve of a particular cylinder of an internal combustion engine includes a camshaft rotatable in synchronism with rotation of the internal combustion engine and having at least one cam, and a plurality of cam followers, one of which slidably engages the cam for selectively operating the valves according to a cam profile of the cam. The cam followers are selectively interconnected and disconnected to operate the valve differently in different speed ranges of the internal combustion engine. In different embodiments, the camshaft has an annular raised portion and low- and high-speed cams, or low-, medium-, and high-speed cams, or an annular raised portion and a cam, and the cam followers are held in sliding contact with these raised portion and cams.

Abstract: A valve operating mechanism for operating a plurality of valves of a particular cylinder of an internal combustion engine includes a camshaft rotatable in synchronism with rotation of the internal combustion engine and having at least one cam. At least one of a plurality of cam followers slidably engages the cam for selectively operating the valves according to a cam profile of the cam. The cam followers are selectively interconnected and disconnected to operate the valves in different speed ranges of the internal combustion engine, the speed ranges including a range in which all of the valves remain inoperative. The camshaft has one or two annular raised portions in addition to the cam, and the cam followers include one or two cam followers which slidably engage the raised portion or portions. The valves remain inoperative by the annular portion or portions and are operated in a high-speed range by the cam, or selectively in low- and high-speed ranges by low- and high-speed ranges.

Abstract: A valve operating mechanism for operating a plurality of valves of an internal combustion engine includes a camshaft rotatable in synchronism with rotation of the internal combustion engine and having an array of three cams including a high-speed cam positioned at one end of the array. Three cam followers are held in sliding contact with the cams, respectively, for operating the valves according to cam profiles of the cams. The cam followers are selectively interconnected and disconnected to operate the valves at different valve timings in different speed ranges of the internal combustion engine. The speed ranges include a high-speed range in which all of the valves are controlled by the cam profile of the high-speed cam. The three cams may include low- and medium-speed cams, or two identical or different low-speed cams, in addition to the high-speed cam.

Abstract: A valve operating mechanism for operating at least one valve of an internal combustion engine, includes a camshaft rotatable in synchronism with rotation of the internal combustion engine and having a pair of low- and high-speed cams of different cam profiles, a rocker shaft, and a pair of first and second rocker arms rotatably mounted on the rocker shaft and operable selectively by the low- and high-speed cams for operating the valve according to the cam profiles of the cams. A selective coupling is operatively disposed in and between the first and second rocker arms for interconnecting the first and second rocker arms in high-speed operation of the engine and for disconnecting the first and second rocker arms from each other in low-speed operation of the engine.

Abstract: A valve operating mechanism includes a camshaft rotatable in synchronism with rotation of an internal combustion engine and having a plurality of cams of different cam profiles. First, second, and third rocker arms are held in sliding contact with the cams, respectively, for operating the valves according to the cam profiles of the cams. The rocker arms are selectively interconnected and disconnected by first and second selective couplings to operate the valves at different valve timings in low, medium, and high speed ranges of the internal combustion engine.

Abstract: A valve operating mechanism for operating a pair of valves of an internal combustion engine, includes a camshaft rotatable in synchronism with rotation of the internal combustion engine and having a first low-speed cam, a second low-speed cam, and a high-speed cam which have different cam profiles, respectively, the first and second low-speed cams being disposed one on each side of the high-speed cam, a rocker shaft, and first, second, and third rocker arms rotatably mounted on the rocker shaft and held in sliding contact with the first low-speed cam, the second low-speed cam, and the high-speed cam, respectively, for operating the valves according to the cam profiles of the cams. A selective coupling is operatively disposed in and between the first, second, and third rocker arms for selectively interconnecting the first, second, and third rocker arms to allow angular movement thereof in unison and disconnecting the first, second, and third rocker arms to allow separate angular movement thereof.

Abstract: A valve operating mechanism for an internal combustion engine having a pair of intake valves or exhaust valves in each cylinder with a first and a second rocker arm corresponding to the pair of valves and a cam for pivoting the first rocker arm. The rocker arms are provided with a connecting mechanism having a piston assembly which is movable between a position in which both said rocker arms are connected and a position in which both said rocker arms are disconnected from each other whereby either both valves of the pair or only one valve may be selectively actuated. A trigger member in the first rocker arm selectively restricts the movement of the piston and a timing cam engages and actuates the trigger member.

Abstract: In an internal combustion engine, an intake manifold has a main distributing chamber and an auxiliary distributing chamber disposed to overlap with the main distributing chamber at a location inward thereof. The main distributing chamber is divided by a partition wall into a primary distributing chamber and a secondary distributing chamber. The partition wall has a boss through which is formed an intake guide passage having one end opening in the auxiliary distributing chamber and directed toward a substantially central location of the chamber. The primary distributing chamber, the secondary distributing chamber and the intake guide passage leading to the auxiliary distributing chamber have respective mixture-inlet ports opening in a carburetor-mounting surface formed on the outer surface of the intake manifold and arranged thereon in a compact array. Thus, the intake guide passage has a simplified configuration, and also the intake manifold can have a compact size.

Abstract: Blow-by gas passages are formed on one side of the cylinder block and cylinder head of an internal combustion engine and spaced longitudinally of its crankshaft. The passages extend from the interior of the crankcase to a location above an upper face of the cylinder head, one of the passages being provided with a mounting port for an oil separator. The other blow-by passage is also connected to the separator, and the separator is connected to the intake system of the engine.

Abstract: A valve operating mechanism for operating a plurality of valves of a particular cylinder of an internal combustion engine includes a camshaft rotatable in synchronism with rotation of the internal combustion engine and having at least one cam. At least one of a plurality of cam followers slidably engages the cam for selectively operating the valves according to a cam profile of the cam. The cam followers are selectively interconnected and disconnected to operate the valves in different speed ranges of the internal combustion engine, the speed ranges including a range in which all of the valves remain inoperative. The camshaft has one or two annular raised portions in addition to the cam, and the cam followers include one or two cam followers which slidably engage the raised portion or portions. The valves remain inoperative by the annular portion or portions and are operated in a high-speed range by the cam, or selectively in low- and high-speed ranges by low- and high-speed ranges.