Nissan Head Blocks

A “head block” can mean:
Cylinder Head – The top of the engine, containing valves, camshafts, and injectors (especially on diesel engines).

Engine Block – The lower portion of the engine housing pistons, crankshaft, and main bearings.
Long Block – A full assembly of head + block (usually with camshaft, crankshaft, pistons, and sometimes timing components). Ideal for engine swaps or complete rebuilds.