In an internal combustion engine, the engine block is the structure which contains the cylinders and other components. In an early automotive engine, the engine block consisted of just the cylinder block, to which a separate crankcase was attached. Modern engine blocks typically have the crankcase integrated with the cylinder block as a single component. Engine blocks often also include elements such as coolant passages and oil galleries. The term "cylinder block" is often used interchangeably with "engine block", although technically, the block of a modern engine (i.e. multiple cylinders integrated with another component) would be classified as a monobloc. Construction The main structure of an engine typically consists of the cylinders, coolant passages, oil galleries, crankcase, and cylinder head(s). 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 monobloc engine blocks has been a gradual progression since the early 20th century. 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 its flathead V8 engine. Those techniques were then applied by other manufacturers to their engines. Cylinder block A cylinder block is the structure which contains the cylinder, plus any cylinder sleeves and 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. In early engines with multiple cylinder bankssuch as V6, V8, or flat-6 engineseach bank was typically made of one or multiple separate cylinder blocks. Since the 1930s, mass production methods have developed to allow both banks of cylinders to be integrated into the same cylinder block. Cylinder liners Wet liner cylinder blocks use cylinder walls that are entirely removable, which fit into the block by means of special gaskets. They are referred to as "wet liners" because their outer sides come in direct contact with the engine's coolant. In other words, the liner serves as the entire cylinder wall, rather than being