Buick LeSabre 1965 Service Manual page 35

ENGINE
ENGINE DESCRIPTION 2 - 1 3
THRUST
BEARING —,
COUNTER WEIGHTS
OIL SEALS
THESE BEARINGS
IDENTICAL
Figure 2-5—Engine Crankshaft
and Bearings
in the two upper grooves of piston
are distinguished by a bevel cut
around the inner edge on one
side. The rings are installed with
identification mark up.
The oil ring in the lower groove
consists of two thin steel rails
separated by a spacer and backed
by an expander placed in the
piston groove. The r a i l s and
spacer of a new ring are lightly
held together with a cement which
dissolves and releases the parts
when oil is applied at start of
operation.
d. Cylinder Heads
Both cylinder heads are identical
except for treatment of the water
inlet ports which exist in both
ends of each head. When a head
is prepared for installation on one
bank of cylinders, the water inlet
port on the rear end is plugged
and the front port is left open for
connection to the water pump.
CONNECTING
ROD
/-RIBS
y-
n
^CAP
BOSSES,
\?\
mi
PISTON-
il t
Figure 2-6—Connecting Rod and
Piston Assembly
This places the plugs in opposite
ends of the right and left heads;
therefore, the heads cannot be
interchanged.
All valves are mounted vertically
in the cylinder head and in line
from front to rear, so they oper-
ate at 45 degrees to the centerline
of cylinders. The angle and loca-
tion of the inlet valve and port
c a u s e s the incoming fuel-air
charge to sweep angularly down-
ward to one side of the cylinder
centerline, resulting in a whirling
action which thoroughly mixes the
charge and produces a beneficial
turbulence during the compres-
sion stroke.
With the spark plug located cen-
trally in top of the combustion
chamber the point gap is well
exposed to the sweep of the in-
coming charge. This reduces the
concentration of exhaust gases
that may have remained in this
area after exhaust of the previous
charge. As noncombustible ex-
haust products are removed frorn
the area around the spark plug the
tendency toward misfiring at part
throttle is reduced.
The central location of the spark
plug causes burning of the fuel
charge to proceed uniformly out-
ward in a l l directions toward
edges of the combustion space.
The short flame travel speeds up
the combustion process, causing
the fuel mixture to burn in a
shorter period of time than that
at which detonation is likely to
occur. High turbulence on the
compression stroke and short
flame travel following ignition
permits the use of a high com-
pression ratio with present day
fuels.
e. Camshaft and Valve
Mechanism
The camshaft is located in the
angle of the cylinder block above
the c r a n k s h a f t where it is
supported in five steel-backed,
babbitt - lined b e a r i n g s . It is
driven from the crankshaft by
sprockets and a single outside
guide type chain. See Figure 2-7.
Hydraulic valve lifters and solid
one-piece steel push rods are
u s e d to operate the overhead
rocker arms and valves of both
banks of cylinders from the single
camshaft. This system requires
no lash adjustment at time of
assembly or in service; there-
fore, no adjusting studs or screws
are provided in the valve train.
Construction and operation of the
hydraulic valve lifters are de-
scribed in subparagraph f below.
The eight rocker arms for each
bank of cylinders are mounted on
a tubular steel shaft supported on
the cylinder head by four die cast
brackets. The rocker arms are
die cast aluminum with inserts
at the push rod socket and the
valve stem contact face. See Fig-
ure 2-8. The rocker arms are
offset to accommodate the differ-
ent planes of movement of the
valves and the push rods which
pass through the cylinder head to
one side of the valves.
The valves operate vertically in
guides pressed into the cylinder
head and each valve has two con-
centric springs to insure positive
seating throughout the operating
ROCKER
: /
j
ARM • ; »
CHAIN S 1
--VALVES-
CAMSHAFTy
WE?
'. T ^ \ VALVE
w
U F T E R
^-SPROCKETS
Figure 2-7—Valve Mechanism