* Camshaft: This rotating shaft has lobes (bumps) that push on the valve lifters. It's driven by the crankshaft.
* Valve Lifters (Tappets, Pushrods, Hydraulic Lifters): These transfer the motion from the camshaft to the valves. Different engine designs use different types: solid tappets, hydraulic lifters (self-adjusting), and pushrods (connecting tappets to rocker arms).
* Rocker Arms (or Rocker Shafts): These are lever-like components that transfer the motion from the lifters to the valves (in overhead valve engines). Some engines have direct-acting lifters where this step is skipped.
* Valves (Intake & Exhaust): These are the components that open and close to let the air-fuel mixture in and exhaust gases out. They are typically spring-loaded to close.
* Valve Springs: These hold the valves closed against the force of the camshaft.
* Valve Guides: These keep the valves centered and aligned in the cylinder head.
* Valve Seals: These prevent oil from leaking past the valve stems.
Some valve trains also include:
* Pushrods: These connect the camshaft to the rocker arms in some overhead valve (OHV) engines.
* Rocker Arm Shafts: These support the rocker arms.
* Valve Adjusters (shims): Used to set the correct valve lash (clearance) in some engines.
The specific components and their arrangement vary depending on the engine type (OHV, OHC, etc.) and design.
