Both big-block and small-block Chevrolet engines most commonly have engine casting numbers located at the rear of the engine near the engine's interface to the transmission. The casting numbers are visible near the top of one of the engine's cylinder banks, though it may be necessary to move hoses or other components to see them in some cars. Once the casting number is located, it is possible to find information about the engine by decoding the casting number.
Casting numbers for Chevrolet big-block engines uniquely identify the engine type and intended use of the engine and may contain additional information about the engine's unique features. For example, a code of 12561358 indicates a Generation VI big-block engine displacing 502 cubic inches and using four mounting bolts, while a code of 24502504 indicates a Generation V 454-cubic inch, four-bolt race-prepped motor with a short deck height of 9.2 inches. There is no obvious structure to these codes, so the only way to understand them is to consult a reference of Chevrolet engine codes.
Big-block Chevrolet engines were primarily manufactured from the 1950s until the 1970s. After that time, Chevrolet's small-block engines became the dominant engine choice for most General Motors vehicles using V-8 engines. However, many modern "small-block" engines are as large or larger in terms of displacement as big-block engines.