All pistons are equipped with two compression rings and one oil scraper ring. The outer surface of the upper compression ring is chrome-plated, and the cross section of the lower compression ring is trapezoid. The bottoms of the pistons of a gasoline engine have an elevation in the middle, as shown by the segment «X» (see illustration). If it is necessary to replace the piston, the height «X» new piston must match the height «X» old piston.
9.1 The amount of elevation on the bottom of the piston of gasoline engines is different. Value «X» should always be measured before installing new pistons