Piston head and piston head assembly

A piston head assembly, comprising:

• a piston head comprising:
• an upper portion comprising:
• an outer wall, and
• an inner wall disposed radially inward of the outer wall,
• wherein a cooling gallery is at least partially defined between the outer wall and the inner wall;
• and
• a lower portion extending downward from the upper portion, the lower portion comprising:
• an upper surface, and
• a skirt extending from the upper surface, the skirt defining a pin bore centered around a pin bore center axis, a portion of the skirt between the pin bore center axis and a skirt reference axis having a curved vertical profile, the skirt reference axis intersecting the pin bore center axis;
• and
• a plurality of lock plates coupled to the upper portion, each lock plate extending between the outer wall and the inner wall, wherein the cooling gallery is defined between the outer wall, the inner wall, and the plurality of lock plates.