What does it mean when you re-bore an engine?
You - re do the Engine , they put new sleave`s into the block , maybe to modify it or to fix a broken or cracked sleave. interesting fact you can put chrome pistoms into a block instead of the normal alloy.... it will improve over all performance.
Re-boring involves machining material from the walls of the cylinders. The purpose of this is to remove the rough surface left behind from the engines rings. It leave a clean surface that is honed to allow for the new set of rings to seal properly. Sleeves are only used when the cylinder wall become too thin to be bored or the old ones have been damaged in some way.