Piston pin offset.

The pin ofset is determined by the location of the pin hole, during manufacture. It is used to put a little more side loading on the piston, to quiet noise before the engine reaches normal temp. The only consideration for the engine builder, is to install the piston, with the marking facing to proper way (usually toward the front). Racing pistons do not have pin offset. Back in the old days, in class racing that required using stock pistons, we would install the pistons backwards, to reduce side loading, and supposidly fre up small amount of horsepower.