a piston for an internal combustion engine has a trunk portion and a crown portion slidably mounted above the trunk portion . the entirety of the trunk portion extends above the piston &# 39 ; s wrist pin bore . a resilient element positioned the crown portion with respect to the trunk portion with sufficient force in a direction tending to separate the crown portion and trunk portion such that the crown portion will be placed in a position of maximum extension during at least some part of the combustion cycle .