so i have been looking at all the different types of forged pistons and noticed that all of them are directional in terms of how they sit in the cylinders. can someone explain to me why this is and what would happen if they were put in backwards?

 

I think sometimes the pin is slightly offset so it needs to be oriented properly. I don't know if this always the case though.

 

offset wrist pins on some and also valve reliefs are different size