C6.4 Remanufactured Engine Assembly — Core Exchange for CAT 320D & 323D Excavators A genuine remanufactured C6.4 engine assembly supplied on an exchange basis: the removed engine returns as a core, and the unit you receive carries zero running hours. Remanufactured assemblies typically price at 40–60% of new and carry a warranty term comparable to a new unit — provided the core arrives complete and reusable, otherwise a graded surcharge applies. This page explains what