just said crank balanced... i assume they had the whole block apart too for resurfacing and what not but im speculating... not sure how it works to be honest. I think they must put the crank on a balancing machine by it self. not sure if they would add the oem harmonic balancer on it as well... I guess that would make sense in a way to do so? But i guess you might as well connect all the rods and pistons to the crank and balance that too? LOL...