An adjusting screw to obtain the specified clearance at the end of the valve stem (tappet clearance). The screw may be in the top of the lifter , in the rocker arm , or in the case of the ball joint rocker arm, the nut on the mounting stud acts in place of a tappet screw.
VALVE TAPPET
Meaning of VALVE TAPPET in English
English dictionary of automotive terms. Английский словарь автомобильных терминов. 2012