A method for automatically setting valve clearances in internal combustion engines (also known as "tappet setting" or "valve lash setting") comprises a series of steps in which a rocker arm (10) is set to a zero position which is recorded as a reference datum and an adjustment screw (18) is then operated to set the rocker arm to a first reference position. The adjustment screw is then rotated through a predetermined angle so that the rocker arm is moved to a second reference position. The difference between the first and second reference positions and the predetermined angle are used to determine a coefficient relating the angular movement of the adjustment screw to linear movement of the rocker arm. The coefficient is then used to calculate the angular rotation of the adjustment screw required to set a predetermined valve clearance relative to the zero position. The initial adjustment of the rocker arm position serves to neutralise backlash in the valve drive train prior to setting the valve clearance.