Subclass 1/255: Valve-gear or valve arrangements, e.g. lift-valve gear (lift valve and valve seat assemblies per seF01L 3/00; slide-valve gear F01L 5/00; actuated non-mechanically F01L 9/00; valve arrangements in working piston or piston-rod F01L 11/00; modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations F01L 13/00) Adjusting or compensating clearance, i.e. lash adjustment automatically by fluid means, e.g. hydraulically Hydraulic tappets between cam and rocker arm