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The engine cylinder block, or "block" is cast in one piece. Usually,
this is the largest and most intricate single piece of metal in the
automobile. Even when the cylinders, cylinder heads, or cylinder
sleeves are separate pieces, the crankcase is still the largest
single part in the engine. Almost all of the engine parts are
attached to the crankcase, directly or indirectly.
The crankcase houses the crankshaft and often the camshaft as well.
With the oil pan, which goes on the lower surface of the crankcase,
it forms an oil-tight housing in which the rotating and reciprocating
parts operate. The cylinder block is laced with coolant passages,
called the "water jacket". The cylinder block is usually made of high
grade cast iron with alloys to improve wear of the cylinders, but
many are aluminum. Plastic blocks have been developed but are not yet
used in production cars. This major unit must be extremely strong and
rigid to avoid bending and stretching. It also varies in thickness
and does not always cool uniformly to prevent warpage by internal
stresses of the cylinder bores.
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