Engine Block contains a cast that holds the crankshaft on the lower part. The cylinder bore is honed and on top of the block where the cylinder head will be installed. It is the heaviest part of the engine. The cylinder block is the foundation of the engine. All other engine parts are assembled in or attached to the cylinder block. Most blocks are cast from gray iron or iron mixed with other metals such as nickel and chromium. It also has water jackets and coolant passages wherein water jackets are the spaces between the cylinder bores and the outer shell of the block.