pistons

I use the KBs on pretty much anything in terms of a milder build. They run a tighter piston to wall clearance which creates a more stable ring over time, they are lighter which as noted is only good, they have the deeper valve reliefs (compared to a factory piston), and the higher top ring reduces wasted space in the chamber. I don't see anything particularly "wrong" with the SP. I just prefer the KBs for those reasons. That beign said - the builder has to know they need the tight piston to wall and make sure the machine shop gets it right or they may be loud. It's not the piston - it's the bore that gets tighter as things get warm. They also have to know about the top ring issue - or you get the broken ring land as pictured above. That's from either a mistake, or detonation. Not the piston's fault in either case.