This assembly of rods, links, cams, and levers actuates the inlet and exhaust valves on reciprocating engines. In steam applications, it dictates exactly when steam enters the cylinder and when it exhausts, allowing operators to reverse direction and adjust power output by shifting the cutoff point. On internal combustion engines, the term covers the camshaft, pushrods, rocker arms, and lifters that synchronize valve motion with the crankshaft.
We need to inspect the valve gear on the number three cylinder because the exhaust timing is lagging.
A poorly lubricated valve gear will quickly wear down the cam lobes or linkages, throwing off the timing and significantly reducing engine efficiency.
Also heard as
- valvetrain
Related terms
Poppet valve
A directional valve consisting of a flat disk on a stem that lifts away from its seat to permit flow.
Pushrod
A rigid metal shaft that transmits linear motion from a cam to a valve or lever.
Cylinder
The tubular chamber in which a piston travels to compress a fluid or convert fluid pressure into mechanical work.
Crosshead
A sliding block that connects a piston rod to a connecting rod, absorbing lateral forces.