Definition
The complete set of mechanical components in a reciprocating engine that opens and closes the intake and exhaust valves in time with the pistons. In a typical aircraft engine this includes the camshaft, cam followers (lifters), pushrods, rocker arms, valves, valve springs, and the keepers that hold the valves in place.
Plain English
All the moving parts that work together to open and close an engine's intake and exhaust valves at the right moment in each cylinder's cycle.
Context Anchor
Seen in aircraft piston engine descriptions, maintenance manuals, engine inspections, and discussions of valve or compression problems.
Derivation
A 'train' in mechanical use means a connected series of parts that pass motion from one to the next — like a gear train. The valve train is the chain of parts that carries motion from the camshaft all the way out to the valve.
Why Pilots Care
Valve train condition directly affects engine power, smoothness, and reliability; wear or improper clearance can cause power loss or catastrophic engine failure.
Intuition Check
“Train” does not mean a railroad train here. It means a linked set of engine parts that work together to move the valves.
Example Sentence 1
The mechanic traced the rough idle to a worn lobe in the valve train.
Example Sentence 2
Excessive play in the valve train produced a loud ticking sound that the pilot noticed on the next flight.