Under no circumstances should a hammer be used on the piston pin pilot and driver when installing a piston pin. Immersing the piston in boiling water for a minute or two will expand the piston pin hole sufficiently to permit easy installation.
To correctly install pin first insert the piston pin pilot and driver through piston pin hole as shown in Fig. 618, then place pin over end of pilot (see Fig. 619) and push piston pin into place.