What does it mean to bore over an engine Does boring over provide for any extra performance?

Boring out the cylinders enables you to put larger diameter pistons in the block. Having a larger diameter cylinder means that the displacement of the engine increases. This increase can provide greater horsepower. Boring out a worn-out engine a few thousandths of an inch can square up the bore of the cylinder and breath new life into a worn out engine by restoring its compression. Good compression will have greater effect on improving the performance than the slight gain in displacement.