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.

Under a tree, in a remote corner of the earth, there is a guy adjusting his hydraulic valve lash with the valve cover off and the engine running. Yes, it's true. We've seen it. Proof is that you can ...

Mechanical lifters were once commonplace in internal combustions engines, but they've been mostly replaced by hydraulic lifters, which offer a lot of benefits.