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ENGINE FUEL AND EXHAUST SYSTEMS
ADJUSTMENTS-REPLACEMENTS
3-15
Figure
3-19-Adiustment
for Smooth Idle
1. With throttle stop screw and idle needle
valves at the initial settings as described above,
start
the engine and run it until it is at normal
operating
temperature.
2. Carefully turn both idle needle valves
"IN" (clockwise) exactly the same amount
until engine begins to roll or run unevenly.
3 Carefully turn both needle valves "OUT"
(counterclockwise) exactly the same amount
until engine again starts to roll or run
unevenly.
4.
Turn both needle valves "IN" one-half the
distance between the first and second
positions,
being careful to turn both valves an equal
amount. See figures 3-19. This should give the
smoothest idling point. NOTE: As the needle
valves
are chang
ed,
th
e
throttle stop screw also
must be chang
ed
to maintain engine idling
speed at 450 RPM
(
8
MPH on level road in
third speed).
5.
If
outside temperature is much colder than
shop where adjustment is
made,
turn both
needle valves "OUT" a slight amount to com-
pensate for difference in temperature.
Final adjustment of the carburetor idle
needle valves also may be made with the aid of
a combustion tester, tachometer, or vacuum
gauge.
When such instruments are used, be
sure t
hey
are
in good condit ion and are used in
accordance with the instructions of the
manu-
facturer.
Regardless
of the m
ethods or
instruments
used
for making adjustments in the shop, the
correctness
of adjustment should be finally
checked by a road test for smoothness at idling
speed
,
power on
acceleration,
and freedom
fr~m
sluggishness or fiat spots throughout entire
speed
range.
3-13 CHOKE THERMOSTAT
ADJUSTMENT
It
is desirable to
have
the choke thermostat
set as lean as operating conditions will permit
in order
to
avoid an over rich
mixture
during
engine
warm-up.
The correctness of the ther-
mostat setting can be tested only when the en-
gine and choke thermostatic coil are
cold.
The
carburetor must be properly adjusted
(par.
3-12) and the manifold heat control valve must
be operating properly (par. 3-11)
.
The cold en-
gine should start readily, idle without loading or
rolling, and should accelerate smoothly during
the warm-up period while the chok
e
is
nor-
mally in operation.
The thermostat is calibrated to give
satisfac-
tory performance wit h regular blends of gaso-
line when it is placed at
the "
Nor mal" factory
setting. A "Lean" setting should be used only
when the car is habitually
operated
on highly
volatile fuel. The ne
ed
for this setting will be
indicated by
excessive
loading or rolling of the
engine on warm up, with the choke at the
"Normal" setting and the carburetor
properly
adjusted. A
"
Rich" setting should be used only
when excessive spitt ing occurs on engine warm
up, with the choke at the
"
Nor mal"
setting:
the
carburetor
properly adjusted,
and the mamfold
heat control valve operating properly.
The "Normal"
settings
for Carter and Strom-
berg choke thermostats are given below
.
When
making either a
"
Lean " or a "Rich" setting,
make no
adjustment ex
cept when engine and
th
ermostatic
coil
are
cold. Turn thermostat
housing one mark at a time in required direc-
tion and test the
results,
until the desired per-
formance is obtained.
a. Se"ing of Carter Climatic Control
Thermostat
The plastic thermostatic coil housing has an
INDEX
Figure 3-20-Carter Climatic Control Thermostat at Normal Setting
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