Short block - everything between the cylinder head and the oil pan (excluding those items) Long block - a short block, with mounted and gasket cylinder head, valves, and camshaft A long block is an engine sub-assembly that consists of the assembled short block, crankshaft, cylinder head, camshaft (usually), and valve train. A long block does not include fuel system, electrical, intake, and exhaust components, as well as other components. A long block may include the timing cover, oil pan, and valve covers. A long block engine replacement typically requires swapping out parts from the original engine to the long block. These parts include the oil pan, timing cover, valve covers, intake manifold, emission-control parts, carburetor or fuel injection system, the exhaust manifold(s), alternator, starter, power steering pump (if any), and air conditioner compressor (if any). A short block is an engine sub-assembly comprising the portion of the cylinder block below the head gasket but above t...