Scheme of removing metal from the piston to adjust its mass
The arrows indicate the places where the metal can be removed.
In terms of mass, the pistons of one engine should not differ from each other by more than±2.5 g.
If there is no set of pistons of the same weight group, you can remove some of the metal on the base of the piston pin bosses. The place of metal removal is indicated by arrows in the figure.
Metal removal, however, must not exceed 4.5 mm in depth relative to the nominal piston height (59.40 mm), and the width is limited to a diameter of 70.5 mm.