I have new pistons to pressfit to connecting rods. I know there may be something about their orientation at installation because at least pistons are asymetric. Do they have to be directed with specific side to the front? How do I know which?
The little notch in the top of the piston goes toward the front of the engine regardless of what side of the engine the piston is installed in. Your machine shop will know how to install the pistons to the rods. You just need to remember to point the notches to the front when you assemble it.
Pistons with the notches have offset pins. As oz stated, the notches have to be pointed toward the front and need to be installed as such. No notches, then the pins are centered and can be installed either way.