Abstract: A piston which has a diameter of about 70 to about 100 mm and which is preferably produced with a resistant, malleable alloy having low density (lower than about 3 g/cm.sup.3) and mechanical properties at high temperatures such that a yield stress greater than about 120 Mpa at temperatures of the order of 300.degree. C. to 350.degree. C. is obtained. In the preferred embodiment, the piston is a single piece piston, comprising a head portion of diameter D ranging from about 70 to about 100 mm and a skirt portion downwardly projected from the head portion and inside which is provided a pair of wrist pin bosses, each having a hole with a diameter d and axial extension L for bearing the articulating wrist pin of the piston.