[james schaechter]

This isn't actually controversial.

There are specs on piston types and rods for weights,etc. In general, If it moves, lighter is better. I don't know if anyone could actually tell you how much better it was, but the piston example is a good one. The replacement stuff has a lot of benefits besides weight too. Better quality all of the way around. I would say that if you are building a stocker engine or any quality race engine, the core components need to be the highest quality and the lightest you can legally run and afford.

Even in drivetrain, every real serious effort points to lighter stuff. Alum shocks, lighter axles, lighter spools and gear, transmission parts, lighter clutches, etc. I am sure that there is someone out there that can point to an example to the contrary, but if you walk around the pits and look at cars, talk to racers, you will see what I mean.