Small block engine codes on Chevy trucks, or any Chevy vehicle, are codes that identify the plant where the engine was built, the product date and characteristics of that particular engine. In combination with partial or complete VINs and cast numbers, the codes help identify the origin of the engine.
The engine code for small block engines tells a great deal about the engine. The most critical piece of information contained in the code are the last three characters (typically letters). Those reference the vehicle and application for which that particular engine was built. In some instances an engine code can reference more than one application, in which case cross referencing the casting number and partial VIN is required.