An engine cylinder piston connecting rod subassembly, for use in an
engine, includes a piston (53), a piston pin (52) and a connecting rod
(51). The connecting rod has a piston end portion with a piston pin bore
(62). The piston pin is inserted through the piston pin bore and
oppositely disposed portions of the piston, for securing the piston and
the connecting rod together. Opposite ends of the piston pin bore are
machined or profiled with relief portions (60, 61), to allow for piston
pin deflection and thereby maximize the load carrying capacity, by
providing a greater area of contact. The relief portions can be a curved
surface (65) machined as part of the bore, or a plurality of end-to-end
angled frustoconical surfaces (66a, 66b, 66c). The relief portions are
shaped to correspond to the shape of the corresponding piston pin when
under load during normal engine operation.