Cylinder block

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The cylinder block is a machined casting (or sometimes an assembly of modules) containing cylindrically bored holes for the pistons of a multi-cylinder reciprocating internal combustion engine, or for a similarly constructed device such as a pump. It is a complicated part at the heart of an engine, with adaptions to attach the cylinder head, crankcase, engine mounts, drive housing and engine ancillaries, with passages for coolants and lubricants. The distance between the cylinder bores (midpoint to midpoint) cannot easily be changed since the machining facilities would require extensive modification. Instead, the bore diameter is commonly varied to obtain different engine displacements. This and the minimum thickness of material required between two cylinders are a limiting factor concerning the potential displacement because the bore to stroke ratio has to stay within certain limits.

The size of the distance between the cylinder bores has led to a distinction between the V8 engine families the Detroit Big Three automakers (Ford, GM and DC) have been building since the 1950ies: There are Small-block and Big-block engines. These families differ in respect to the distance between cylinder bores, but not necessarily in displacement since the later is defined by bore and stroke.

Whilst the big-blocks have been less commonly used in recent years, the small-block families have grown in displacement and now reached a level that was reserved for big-blocks in previous years (up to 7 litres of displacement in a Corvette). Even though the technology changed a lot, basic specifications have been the same for up to fifty years now! ([Source: Motortrend])

Cylinder block

See also