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ENGINE
ENGINE DESCRIPTION
MOU
NTING
BRACKET
(ENG
INE)
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l BO
LTING
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PLATE
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M
OUNTING
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PAD
THRUST
PLATE
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MOUNTIN
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PAD
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TRANSM ISSIO
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Figure 2-3-Engine and Transmission Mountings
2-9
ance between the thrust pad and transmission
support.
2-5 ENGINE CONSTRUCTION
a. Cylinder Crankcase, Cylinder Head
and Gaskets
The cylinder block and crankcase are cast in-
tegral to form the cylinder crankcase. This con-
struction, together with liberal reinforcing ribs
also cast integral, provides maximum rigidity
with a minimum size and weight.
The cylinder bores are precision bored and
double honed. The honing operations are con-
trolled to leave minute pockets in the cylinder
walls which are, in effect, small oil reservoirs
which provide efficient piston lubrication.
When one or more bores in a cylinder crank-
case cannot be properly finished to the nominal
size, all bores are finished to .010" oversize and
are fitted with .010" oversize pistons and rings.
This practice is quite general in the automotive
industry and engines having such cylinder
crankcases are not to be considered as special
or other than production standard. These en-
gines are identified for service purposes by a
dash mark about
lA."
long stamped directly fol-
lowing the engine number.
The detachable one-piece cast iron cylinder
head contains the combustion chamber which
are cast in place. The cylinder head mounts the
overhead valve mechanism, spark plugs, intake
and exhaust manifolds, and its attached to the
cylinder crankcase by 22 special
%6"
alloy steel
bolts.
Series 40 engines use a steelbestos cylinder
head gasket which is approximately .050" thick.
Series 50 and 70 engines use a sheet steel gas-
ket which is .015" thick. To insure a tight seal,
the steel gasket is crimped around the edges of
all openings where leakage may occur.
b. Pistons, Pins and Rings
Pistons are Anodized aluminum alloy. They
have full skirts, are cam ground, and have two
transverse slots cut in the skirt below the bot-
tom ring groove and parallel to the piston pin.
Two bosses cast inside the lower end of skirt
below piston pin bosses provide points at which
metal may be removed as required to bring the
piston within the specified weight limit.
The piston head is specially shaped with a
hump on one side
a
nd a rounded depression on
the camshaft
side.
This unusual shape com-
bined with the valve-in-head design forms a
combustion chamber in which the fuel-air
charge is compressed in the form of a flattened
ball at the point of ignition. This "Fireball"
design regulates the burning of the fuel-air
charge and smooths out
the
power impulses.
See figure 2-5.
Grooves for two compression rings and two
oil rings are located above the piston pin. The
oil ring grooves are drilled to provide drain
back of oil to inside of skirt. A groove cut in
the land above the top compression ring acts
as a dam to deflect heat away from the top
ring.
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