Engine casting numbers are identifying marks automobile manufacturers create on the block or head of an engine. These numbers are in the die cast mold and are part of each engine the mold produces. A stamped number on an engine is not the casting number but the serial number.
Casting numbers are useful in identifying the engine in a vehicle. In older automobiles, owners often exchange engines. Although the engines within a line are often interchangeable, each requires parts that are specific to the particular engine casting. Using the casting number, when the owner is not familiar with the history of the vehicle ensures selection of the correct parts.