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An overhead valve engine, abbreviated (OHV) and sometimes called a pushrod engine, is a piston engine whose valves are located in the cylinder head above the combustion chamber. This contrasts with flathead (or "sidevalve") engines , where the valves were located below the combustion chamber in the engine block .
SOHC design (for a 1973 Triumph Dolomite Sprint) . The oldest configuration of overhead camshaft engine is the single overhead camshaft (SOHC) design. [1] A SOHC engine has one camshaft per bank of cylinders, therefore a straight engine has a total of one camshaft and a V engine or flat engine has a total of two camshafts (one for each cylinder bank).
The ratio is determined by the ratio of the distances from the rocker arm's pivot point to the point where it touches the valve and the point where it touches the pushrod/camshaft. A rocker ratio greater than one essentially increases the camshaft's lift. Current automotive design favors rocker arm ratios of about 1.5:1 to 1.8:1.
Pushrods are long, slender metal rods that are used in overhead valve engines to transfer motion from the camshaft (located in the engine block) to the valves (located in the cylinder head). The bottom end of a pushrod is fitted with a lifter, upon which the camshaft makes contact. The camshaft lobe moves the lifter upwards, which moves the ...
On most overhead valve (OHV) engines, proper clearance between the camshaft and tappet is achieved by turning a set screw in the end of the rocker arm that contacts the end of the pushrod until a desired gap is achieved using a feeler gauge. Too large a gap results in wear from misaligned parts and compromised engine performance, and too small ...
The Mitsubishi Saturn or 4G3 engine is series of overhead camshaft (OHC) straight-four internal combustion engines introduced by Mitsubishi Motors and saw first service in the 1969 Colt Galant. Displacement ranges from 1.2 to 1.8 L (1,239 to 1,755 cc), although there was also a rare 2-litre (1,994 cc) inline-six version built from 1970 until 1976.
A single camshaft located in the engine block uses pushrods and rocker arms to actuate all the valves. OHV engines are typically more compact than equivalent OHC engines, and fewer parts mean cheaper production, but they have largely been replaced by OHC designs, except in some American V8 engines.
The lobed camshaft rhythmically presses against the lifter, which transmits the motion to the engine valve in one of two ways: through a pushrod which actuates the valve via a rocker mechanism (in an overhead valve (OHV) engine); via direct contact with the valve stem or rocker arm (in an overhead camshaft (OHC) configuration).