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1-10
Chapter
1
General Engine Service
distribute
the
oil
and repeat
the
compression
test.
The
oil
will
temporarily
seal
leakage
past
the
rings.
If ap
proximately
the
same
reading
is
obtained,
the
rings are
satisfactory,
but
the
valves
are
leaking.
If
the
com
pression
has
increased
10
pounds
or
more
over
the
original
reading,
there
is leakage
past
the
rings.
During
a
compression
test,
if
the
pressure
fails
to
climb
steadily
and
remains
the
same
during
the
first
two
successive
strokes,
but
climbs
higher
on
the
suc
ceeding
strokes,
or
fails
to
climb
during
the
entire
test,
it
indicates
a
sticking
or stuck
valve.
Exhaust
Gas Analysis
An
exhaust
gas
analysis
is
a
method
of
testing
the
ratio
of
fuel
and
air
entering
the
cylinders,
and
the
adjustment
and
performance
of
the
carburetor.
How
ever
it
cannot
be
used
to
calibrate
a
carburetor.
As
there
are
various
types
of
analyzers,
follow
the
instructions
of
the
manufacturer.
On
a
dual
exhaust
system,
install
the
analyzer
in
the
outlet
pipe
opposite
the
side
of
the
system
that
contains
the
exhaust
gas
control
valve.
For
example,
if
the
valve
is
on
the
right
side,
install
the
analyzer
in
the
left
muffler outlet pipe.
3. MANIFOLDS
AND EXHAUST GAS CONTROL VALVE
Hot
exhaust gases
are
diverted into
the
intake
mani
fold
to
provide
the
heat
necessary
to
vaporize
the
in
coming
fuel-air
mixture and
to
minimize
engine
stalling
and carburetor
icing during
cold
engine operation.
The
hot
exhaust gases are
directed into
the
intake
manifold
by
a
thermostatically
controlled
valve
located in
the
exhaust manifold.
On
the
6-cylinder
engine, the
hot
exhaust
gases
are
directed into
a chamber
(heat riser)
which
is
cast
into
the
intake
manifold
section
where
the
carburetor
and
exhaust manifold are
attached.
All
8-cylinder intake
manifolds
contain
a
passage
through
the
center
section
and
under
the carburetor,
through
which
the
hot
exhaust
gases
are
directed.
Manifolds
Clean
the
manifolds
in
a
suitable
solvent,
then
dry
them
with
compressed
air.
Scrape
all
carbon
deposits
from
the
center
exhaust
passage
below
the
carburetor
CLOSED
(HEAT
ON)
OPEN
(HEAT OFF)
heat
riser
of
the
intake
manifolds.
This
carbon
acts
as
an
insulator
restricting the
heating
action
of
the
hot
exhaust gases.
Blow
out
the
automatic
choke
passages
of
the
8-
cylinder
intake
manifolds
with
compressed
air.
Make
sure
the
passages
are
completely open,
otherwise choke
operation will
be impaired.
On
intake
manifolds
used
with
a
four-barrel
car
buretor,
check
the
fresh
air
heat
tube
that
passes
through the
manifold
for
leaks,
as
follows:
Adjust
a vacuum
pump
to
obtain a
steady reading
of
three
inches
of
vacuum.
Block
off
one
opening
of
the
tube
with
a
moistened
finger,
then
connect
the
vacuum
pump hose
to the
other
opening.
If
the
pump does
not
maintain
a
steady reading
there
is
a
leak in
the tube
and
the tube
should
be
replaced.
Inspect
the
manifolds
for
cracks,
leaks,
or
other
de
fects
that
would
make
them
unfit
for further
service.
Replace
all
studs
that
are
stripped
or
otherwise
dam
aged.
Remove
all
filings
and
foreign
matter
that
may
have
entered
the
manifolds
as
a
result
of
repairs.
Exhaust Gas Control Valve
Check
the
thermostatic
spring
to
make
sure
it is
CLOSED
(HEAT
ON)
1001
-A
Fig.
7
Exhaust
Gas Control
Valve
8-Cylinder
Engines
Fig.
2
Exhaust
Gas
Control
Valve
6-Cylinder
Engine
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