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Although an overhead camshaft (OHC) engine also has overhead valves, the common usage of the term "overhead valve engine" is limited to engines where the camshaft is located in the engine block. In these traditional OHV engines, the motion of the camshaft is transferred using pushrods (hence the term "pushrod engine") and rocker arms to operate ...
This reduced inertia in OHC engines results in less valve float at higher engine speeds (RPM). [1] A downside is that the system used to drive the camshaft (usually a timing chain in modern engines) is more complex in an OHC engine, such as the 4-chain valvetrain of the Audi 3.2 or the 2 meter chain on Ford cammers. Another disadvantage of OHC ...
Roller rockers can also be used in overhead cam engines (OHC). However, these generally have the roller at the point where the cam lobe contacts the rocker, rather than where the rocker contacts the valve stem. Some OHC engines employ short rocker arms, also known as finger followers, [2] in which the cam lobe pushes downward on the back of the ...
2.5 L; 152.2 cu in (2,494 cc) inline-5, with two (pushrod-actuated) valves-per-cylinder and indirect fuel injection from either Bosch or Spica. 88 mm × 82 mm (3.46 in × 3.23 in). This engine is a five-cylinder version of the 2-litre HR488, and also uses KKK turbochargers. Applications:
In 1994, all 2.2-liter engines were updated to sequential multi-port fuel injection and power increased to 120 hp (89 kW), with torque increasing to 140 lb⋅ft (190 N⋅m). The MPFI and SFI versions produced enough power to allow the 2.2 to replace the old Pontiac Iron Duke engine as the 4-cylinder offering in the S/T trucks and A-body cars.
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 mated to a lifter, upon which the camshaft makes contact. The camshaft lobe moves the lifter upwards, which moves the pushrod.
Also pushrod engines almost always make less power and torque from a given displacement, compare just about any engine you can find: BMW M3 - 81.875 ft-lb/l, LS7 - 67 ft-lb/l. Also compare the output of the OHC Ford engines to the GM pushrod engines, the Fords have higher torque output for a given displacement.
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.