Before the implementation of hydraulic lifters to keep the engine's valves in proper working order, regular adjustment was required to maintain the critically necessary clearance in the valvetrain.

This is a category that is pretty rapidly going away. You'll be hard-pressed to find an overhead valve — also known as a pushrod — engine in anything outside of a General Motors LS/LT V8 or one of ...

The engines of yesteryear were pretty simple, with tappets clackity-clacking away on cam lobes, opening valves, and making a ruckus while doing it. Mechanical lifters were adequate for valve operation ...