Buick LeSabre 1965 Service Manual page 86

3 - 1 0 DESCRIPTION ENGINE FUEL AND EXHAUST SYSTEMS
without being affected by move-
ment of the engine on its rubber
mountings. See Figure 3-20.
The accelerator pedal is mounted
on two ball studs. Depressing the
accelerator pedal causes the
pedal to make a rolling contact
with a roller on the throttle op-
erating lever, forcing the lower
part of the lever to pivot forward
and down. The lever pivots in a
bearing mounted on the body cowl.
See Figure 3-20.
As the lower part of the throttle
operating lever is pushed forward
by the accelerator pedal, the up-
per part of the lever is pulled
rearward. This pulls the throttle
rod rearward, causing the car-
buretor throttle lever to open the
throttle valves.
The return spring returns the
throttle linkage to idle position
whenever pressure is released
from the accelerator pedal. See
Figure 3-20.
On automatic transmission cars,
a dash pot is mounted in position
to be contacted by an arm of the
carburetor throttle lever as the
throttle is closed. The dash pot
cushions the c l o s i n g of the
throttle valves to prevent engine
stalling when the accelerator
pedal is suddenly released.
On all a u t o m a t i c transmission
cars, a t r a n s m i s s i o n detent
switch is mounted at the full
throttle position of the carburetor
throttle lever. When the throttle
linkage is moved to wide open
throttle position, the switch con-
tacts are closed to cause the
t r a n s m i s s i o n to "downshift".
This switch also has a second set
of contacts which close slightly
before wide open throttle position
to cause the stator blades in the
t r a n s m i s s i o n to "switch-the-
pitch" to high performance angle.
See Figure 3-20.
On all a u t o m a t i c transmission
cars, an idle stator switch is in-
stalled in a joint of the throttle
linkage between the throttle lever
and the throttle rod. Whenever the
throttle linkage returns to curb
idle position, the switch contacts
are closed to cause the stator
blades to "switch-the-pitch" to
high angle. This r e d u c e s the
transmission load on the engine
at idle, thereby r e d u c i n g the
tendency of the car to creep. See
Figure 3-17.
3 - 3 DESCRIPTION OF
INTAKE AND EXHAUST
SYSTEMS
a. Intake Manifold Distribution
A low-restriction, dual (2 section)
intake manifold is bolted to the
inner e d g e s of both cylinder
heads, where it connects with all
inlet ports. The end branches of
each section run at 90 degrees to
the connecting middle branch,
thereby forming a T-junction aj
the dividing point which assures a
uniform division and distribution
of fuel to all cylinder inlets. Each
manifold section feeds four cyl-
inders - two in each bank. See
Figures 3-6 and 7.
The 2-barrel carburetor feeds
one barrel into each section of
its 2 port manifold. The 4-barrel
carburetor feeds one primary and
one secondary barrel into each
section of its 4 port manifold.
Figure 3-6— Intake Manifold
Distribution - 401 and
425 Engines
Figure 3-7—Intake Manifold
Distribution - Dual
4-Barrel Engine
b. Intake Manifold Heat—401
and 425 Engines
The intake manifold is heated and
hot spots are provided at the T-
junction dividing points by cross-
over c h a m b e r s cast along the
outer walls of each end branch.
These chambers connect to the
two middle exhaust passages in
each cylinder head. Hot spots
located at the dividing junctions
aid in vaporizing the heavier par-
ticles of fuel which are swept
against the outer walls due to
their greater momentum. The
heated intake manifold also aids
in obtaining a uniform fuel
distribution.
The intake manifold is heated by
exhaust gas crossover passages
cast under the center section of
the manifold. These passages
connect to the two middle exhaust
passages in each cylinder head.
Exhaust heat is supplied directly
to the carburetor mounting sur-
face by two holes drilled from the
mounting surface into the cross-
over passages. The carburetors
are designed to conduct this heat
around the throttle valve area to
reduce e n g i n e stalling due to
carburetor icing.
A heat control valve with a bi-
metal thermostat is located below