I know this is kinda a n00b question but I don't have much engine building experience. Is it possible to mess up a block by a spun bearing? Basic story is motor had rod knock, motor seized, and found out it had a spun bearing. I understand that the crank and some other things can be damaged but also easily replaced or fixed, but what about the block itself?

 

Did you spin a rod bearing or a main bearing? A spun rod bearing can potentially damage the rod and and the rod journal on the crank. A spun main bearing could potentially damage the crank and the main journal in the block. Depending on the severity of the damage, the crank can be micropolished and the block mains can be line bored/honed.