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ENGINE
ENGINE DESCRIPTION
2-13
Figure 2-8-lnlet and Exhaust Valves-Sectional View
have mushroom heads, all ground for 45 degree
seats.
See figure
2-8.
Each valve is closed by
two coil
springs.
Adjustable lash
valve mechanism is used in
all 1948 Series 40-50 engines and in 1948 Series
70 engines up to No.
5192693.
The valve lifters
are plain
sleeve
type, and the ball studs in
rocker arms are used to adjust valve lash to
specified limits to insure full seating and quiet
operation of valves.
Hydraulic sell -adju sting valve mechanism is
used in 1948
Se
r ies 70
Dynaflow
Drive engines
starting with
No.
5192694, and is used in all
1949 Series 50 and 70 Dynaflow Drive engines.
See subparagraph
I
below.
f.
Hydraulic Valve Mechanism
Engines
equipped
with
hydraulic
valve
mechanism are identified by RED "Buick Fire-
ball" lettering on the rocker arm cover; engines
having adjustable valve lash mechanism have
blue lettering. A label also is placed on rocker
arm cover, stating-"This Engine Equipped
With
Hydraulic
Lifters."
The hydraulic valve
mechanism
employs hy-
draulic lifters which automatically maintain
zero valve lash under all operating conditions.
The ball studs in rocker arms are used only for
the initial adjustment of the hydraulic
lifters.
The construction of a hydraulic
va
lve lifter
is shown in figure
2-9.
The
pl
unger
and the
body are g
round
t
o ver y close limits
and are
selectively fitted to
obt ain f
r ee
movement with
the least possible clea r ance, in order to control
leakage of oil from the lower chamber within
very close limits. The spring exerts a 10 pound
load, which is enough to take up all lash clear-
ances between parts in the valve train without
affecting positive seating of the valve. The
check
valve ball seats in the plunger feed hole
rt
IJ
·11
II
e.
Camshaft and Valve Mechanism
The forged steel camshaft is supported in
the cylinder crankcase in five
steel-backed
bab-
bitt-lined bearings and is driven from the
crankshaft by a silent chain. The camshaft
actuates the overhead valves
through lifters,
push rods, and rocker arms.
The valve lifters operate in guide holes
reamed in crankcase
above
the camshaft. The
tubular steel push rods
have hardened
steel ball
plugs at lower ends which seat in valve lifters,
and hardened steel ball sockets at upper ends
which engage ball studs in rocker
arms.
The
threaded ball studs provide for adjustment and
are locked by hex nuts. The rocker arms pivot
on a tubular steel shaft which is supported
on
the cylinder head by eight
bracket s. Inlet
valves
have st r eamlined h
eads
and
exhaus t valves
Full precision
crankshaft
bearings are
used
in all engines. The bearings are made from
Durex
100-A
material having superior fatigue
qualities. The babbitt lining is
bonded
to the
steel back of the bearing by a fine textured
nickel-copper matrix which gives continuous
support to the bearing metal. No shims or
other means of adjustment are required with
these bearings as they are held to very close
limits on size.
The crankshaft is counterbalanced by weights
.
forged integral with crank cheeks, and
is
both
statically
'
and dynamically balanced
during
manufacture. A flange forged integral
with
rear end of shaft supports the flywheel which
is separately balanced during manufacture.
'The crankshaft in Series 70 engines used
with Dynaflow Drive are not interchangeable
with crankshafts in Series 70 engines used
with Syncro-Mesh transmission. The difference
is in the shape of the flywheel flange and the
counterbore in rear end of shaft.
Flywheels used in Series 40-50 and Series 70
engines employed with
Syncro-Mesh
transmis-
sions are cast iron, machined to form a driving
face for the clutch plate. Flywheels used in
S
eries
70 engines employed with Dynaflow
Drive are flexible steel stampings to which the
Dynaflow primary pump is bolted. Both type
flywheels carry a ring gear for cranking the
engine.
A flywheel type harmonic balancer is mounted
on the front end of crankshaft to dampen tor-
sional vibration. The hub of the balancer is
keyed to the crankshaft and retained by a
clamp bolt threaded into the end of crankshaft.
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