What is the engine block

The engine block is one of the biggest, heaviest and important component of the internal combustion engine. The engine block is fixed on the vehicle body, through passive elastic supports or more advanced active hydraulic dampers. An engine block is sometimes called a cylinder block but it has the same meaning.

The main functions of the engine block are:

  • contains some of the moving arts of the engine: piston, connecting rod, crankshaft
  • contains a part of the cooling circuit
  • together with the cylinder head forms the combustion chamber
  • it is support for a part of the lubrication circuit: oil pan, oil pump, oil filter
  • it is support for auxiliary devices: starter motor, A/C compressor, alternator, intake and exhaust manifolds, etc.

Image: ICE main components

  1. cylinder head cover
  2. cylinder head
  3. engine block
  4. oil pan

The cylinder head is mounted on top of the engine block. It’s fixed using long bolts which pass through the cylinder head and threaded into the engine block. Between the cylinder head and engine block there is a cylinder head gasket which helps sealing the combustion chamber and the cooling circuits.

Depending on the engine, the cylinder block can be a single component or split in two, an upper and a lower block.

Image: Ecotec 2.0L I-4 VVT DI Turbo Aluminium Engine Block Casting
Source: GM

  1. crankshaft fixing support
  2. coolant circuit passage
  3. cylinder
  4. threaded hole (for cylinder head bolts)
  5. lubrication circuit passage
  6. auxiliary equipment support

During engine running there are high mechanical and thermal stress applied on the engine block. The engine block must withstand very high forces, pressures, vibrations and temperatures. The cylinders need to have low friction coefficient but high stiffness. In the same time the engine block mass must be as low as possible.

Image: Ecotec 2.0L I-4 VVT DI Turbo Lower and Upper Aluminium Engine Block Casting
Source: GM

Usually the engine block is manufactured from cast alloyed iron. This is a cost effective solution. The performance engines are manufactured from aluminium alloy, which, compared to iron engine blocks have the following advantages:

  • lower mass
  • higher thermal conductivity
  • better wear resistance
  • are easier to manufacture

The most important disadvantage of the aluminium based engine block is higher cost.

Depending on the cylinder configuration we can have different geometries of engine blocks:

  • vertical engine block (e.g. I-4, GM Ecotec): all cylinders are in single row (straight engines)
  • “V” engine block (e.g. V8, Ford Mustang): with two rows of cylinders (displaced at an angle of 90° – 120°)
  • horizontal engine block (e.g. 4 boxer, Subaru): opposed cylinders at 180° (boxer engine)
  • “W” engine block (e.g. W16, Bugatti Veyron): two “V” cylinder rows displaced at an angle

Image: 7.0L V-8 (LS7) Chevrolet Corvette engine block
Source: GM

The engine block is a static/fixed component of the engine. It’s not very interesting from the vehicle owner point of view but it is a very important component since it holds together most of the engine parts and it has to withstand high amount of mechanical and thermal stress.

For any questions or observations regarding the engine block please use the form below.

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