Cylinder blocks are the foundational structural component of an engine, housing the cylinders where combustion occurs. Typically cast from iron or aluminum alloy, they provide critical cooling passages for temperature regulation. Precision-machined cylinder bores maintain tight tolerances for piston movement and sealing via piston rings. Main bearing journals are integrated within the block to support the crankshaft, while dowel pins ensure precise alignment with other engine components. Oil galleries are cast or drilled into the block to deliver lubrication to critical engine parts.