Long block is an automotive term for an engine sub-assembly that consists of the assembled 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 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 injectionsystem, the exhaust manifold(s), alternator, starter, power steering pump (if any), and air conditioner compressor (if any). - https://en.wikipedia.org/wiki/Long_block