The main structure of an engine (i.e. the long block, excluding any moving parts) typically consists of the cylinders, coolant passages, oil galleries, crankcase and cylinder heads. The first production engines of the 1880s to 1920s usually used separate components for each of these elements, which were bolted together during engine assembly. Modern engines, however, often combine many of these elements into a single component, in order to reduce production costs.
The evolution from separate components to an engine block integrating several elements (a monobloc engine) has been a gradual progression throughout the history of internal combustion engines. The integration of elements has relied on the development of foundry and machining techniques. For example, a practical low-cost V8 engine was not feasible until Ford developed the techniques used to build the Ford flathead V8 engine. These techniques were then applied to other engines and manufacturers.
A cylinder block is the structure which contains the cylinder, plus any cylinder sleevesand coolant passages. In the earliest decades of internal combustion engine development, cylinders were usually cast individually, so cylinder blocks were usually produced individually for each cylinder. Following that, engines began to combine two or three cylinders into a single cylinder block, with an engine combining several of these cylinder blocks combined together.
In early engines with multiple cylinder banks — such as a V6, V8 or flat-6 engine — each bank was typically a separate cylinder block (or multiple blocks per bank). Since the 1930s, mass production methods have developed to allow both banks of cylinders to be integrated into the same cylinder block.