Buick LeSabre 1965 Service Manual page 87

ENGINE FUEL AND EXHAUST SYSTEMS
DESCRIPTION 3 - 1 1
the right exhaust manifold. See
Figures 3-14 and 15. When the
engine is cold and the thermostat
closes the valve, the resulting
back pressure in the manifold
forces exhaust gas through the
crossover passages in the intake
manifold to the left exhaust mani-
fold. As the engine warms up and
the thermostat releases the valve,
the flow of hot gas through the
crossover chamber is reduced.
Restricted openings in the metal
intake manifold gaskets meter the
flow of exhaust gases through the
intake manifold when the engine
is cold and the heat valve is
closed.
c. Exhaust Manifolds,Pipes,
and Mufflers
Each cylinder exhausts through an
individual port into a separate
branch of the exhaust manifold.
This manifold, referred to as the
double "Y" type, is designated to
provide a separation of 270 de-
grees crankshaft rotation between
any two exhaust impulses in one
branch of the m a n i f o l d . This
elimination of overlap within any
given branch of the manifold per-
mits valve timing that improves
engine efficiency, minimizes ex-
haust valve burning, and effects
more complete scavanging of ex-
haust gas from the cylinder.
The right manifold contains the
carburetor choke heat stove which
consists of an alloy steel heating
tube mounted in two drilled holes
in the manifold. Heated air is
drawn from the heat stove through
an insulated pipe into the auto-
matic choke housing.
All front and center exhaust pipe
assemblies are made up of two
layers (inner and outer) of welded
pipe. Rear exhaust pipes and tail
pipes use single layer pipe. The
double layer pipe is used to muf-
fle pipe "ring" which is set-up
by the firing impulses of the in-
dividual cylinders; the life of the
pipe is also greatly increased.
Most of the connections are of the
ball joint type. These ball joints
make for easy disconnection, con-
nection, and alignment of the ex-
haust system without damage to
the parts. No gaskets are used in
the entire exhaust system. Con-
nection of the tail pipe to the
muffler is made with a U-bolt and
clamp.
The muffler is of the oval-shaped,
dynamic flow type having very low
back p r e s s u r e . It is double
wrapped of heavy gauge galva-
nized steel with a layer of asbes-
tos placed between wrappings to
aid in reduction of noise transfer
and to prevent any "oil-canning"
effect. The exhaust system is
supported by free hanging rubber-
fabric mountings which permit
free movement of the system but
do not permit transfer of noise
and vibration into the passenger
compartment.
d. Dual Exhaust System
The dual exhaust system is op-
tional on Series 45-46-48 cars.
Dual e x h a u s t is standard on
Riviera models.
In Rivieras, a single muffler is
placed crosswise at the rear of
the car. See Figure 3-11. The
muffler has an inlet and an outlet
on each end. Each side of the dual
exhaust system has a front ex-
haust pipe assembly having a
resonator at the rear end. Each
resonator is attached by a U-bolt
and clamp. Each side has a short
rear exhaust pipe just forward of
the rear spring cross member.
Each rear exhaust pipe is at-
tached to the muffler inlet by a
ball joint. A tail pipe is attached
to each of the muffler outlets by
a U-bolt and clamp. The muffler
is supported by the rear exhaust
pipe and tail pipe hangers. See
Figure 3-11.
The exhaust gases from each bank
of cylinders pass through indi-
vidual resonating chambers in the
muffler and then enter one com-
mon c h a m b e r . This common
mixing of gases increases muffler
silencing ability and eliminates
the "cold side" muffler.
In Wildcats and Electras, there
are two m u f f l e r s and two
resonators. See Figure 3-10.
e. Single Exhaust System
The single exhaust system has a
front exhaust pipe assembly con-
sisting of a branch pipe from each
exhaust manifold welded together.
A long center exhaust pipe ex-
tends back to the muffler. The
rear exhaust pipe extends up over
the rear axle to the resonator. A
short tail pipe extends back from
the resonator. See Figures 3-8
and 9.
None of the p a r t s are inter-
changeable between the single and
dual exhaust systems except for
some of the hangers. However,
both right and left exhaust mani-
folds are the same for single or
dual exhaust cars.