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TM 9-8000
(2)  Providing a flange at the top of the block
that locks the sleeve in place when the cylinder
head is bolted into place. This is more desirable
than a friction fit, because it locks the sleeve
(3)  Casting the sleeve into the cylinder
wall. This is a popular means of securing the
sleeve in an aluminum block.
Whatever method is used to secure the sleeve, it is
very important that the sleeve fits tightly. This is
important so that the sleeve may transfer its heat
effectively to the water jackets.
e. Crankcase (Fig. 3-4). The crankcase is
the part of the cylinder block that supports and
encloses the crankshaft. It is also where the
engine's lubricating oil is stored. The upper part
of the crankcase usually is part of the cylinder
block, while the lower part is removable. This
Figure 3-2. Requirements of a Cylinder.
removable lower part usually is called an oil pan,
and is made of cast aluminum or pressed steel.
This will increase engine life while keeping pro-
duction costs down.
f.  Cooling and Lubrication (Fig. 3-1). The
cylinder block also provides the foundation for the
(2)  Because the cylinders wear more than
cooling and the lubrication systems. It provides
any other area of the block, the life of the block can
the mountings for the pumps, and has the coolant
be extended greatly by using sleeves. When
and lubrication passages cast into it.
overhaul time comes, the block then can be
renewed by merely replacing the sleeves. For this
3-2. Cylinder Heads.
reason, sleeves are very popular in large diesel
engines, for which the blocks are very expensive.
a. General (Fig. 3-5). The cylinder head is a
(3)  As stated in paragraph 3-lb., using a
separate one-piece casting that bolts to the top of
sleeve allows an engine to be made of a material
the cylinders on an air-cooled engine, or to the
such as aluminum by providing the wearing
top of the cylinder block on a liquid-cooled
qualities necessary for the cylinder that the
aluminum cannot.
b. Construction.
There are two types of cylinder sleeves: the wet
and the dry type. The dry type is a sleeve that
presses into a full cylinder that completely covers
(1)  The cylinder heads on liquid-cooled
the water jacket. Because the sleeve has the block
engines have been made almost exclusively from
to support it, it can be very thin. The wet sleeve
cast iron until recent years. Due to weight
also presses Into the cylinder. The difference is
considerations that have become more Impor-
that the water jacket is open in the block and is
tant, a large percentage of cylinder heads now
completed by the sleeve. Because it gets no
are being made from aluminum.
central support from the block, the wet sleeve
must be made thicker than a dry sleeve. Also,,
(2)  The cylinder heads on air-cooled en-
because the sleeve completes the water jacket, it
gines are made almost exclusively from alumi-
must fit so as to seal in the coolant. The following
num. This is due to the fact that aluminum will
are the three basic ways of securing the sleeves in
conduct heat approximately three times as fast as
the cylinder block:
cast iron. This is a critical consideration with air
(1) Pressing in a sleeve that is tight enough
to be held in by friction.


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