I believe that rebuilt is often your own part (or engine) and a reman part is a part in exchange. Remanufactured parts are rebuilt in larger series, for example a machine shop rebuilds a large series of the same engine keeping the cost for setting up their machines low. If they will rebuild a Ford V8, than a V6 Chevy after that, a big block Chevy after that it takes a lot more time than if they could do 50 small blocks in a row.
