Complex sentence: In the 567,645, and 710 engines the number refers to the displacement of each cylinder in cubic inches, while the H-Engine's "265" designation refers to the bore of the cylinder in millimeters.
Split into simpler sentences: In the 567,645, and 710 engines the number refers to cubic-inch displacement of each cylinder. The H-Engine's "265" designation refers to the cylinder bore diameter in millimeters.