Long block

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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 (see below for a more complete list).

  • Short block. The long block is always a superset of the corresponding short block.
  • Cylinder head. A cylinder head assembly is installed with a head gasket and torqued to specification. Complete cylinder heads include valves, valve springs, valve guides (if applicable), valve seats (if applicable), valve locks, and valve keepers. Flathead engines include the valve train if it didn't come with the short block.
  • Camshaft in most engines. On many engines with timing gears, the camshaft is timed.
  • Oil pan and possibly 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).

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