6C-2
1968
PONTIAC
SERVICE
MANUAL
80%
of 96 Is 77.
While
all cylinders are
well
above
77,
they are all excessively low. This indicates all
poor valves or, If accompanied by oil consumption,
worn
rings or low crank
speed.
If compression is
subnormal, tune-up
will
probably not be satisfactory.
(See specifications at end of section 6 for correct
compression
pressures.)
NOTE:
The compression check is important be-
cause
an engine with low or uneven compression
cannot be tuned successfully to give peak per-
formance.
Therefore,
it is essential that improper
compression
be
corrected
before proceeding with
an engine tune-up.
CLEAN,
TEST
AND
INSTALL SPARK PLUGS
1.
Inspect
each
plug
Individually
for badly
worn
electrodes, glazed, broken or blistered porcelains
and replace plugs where
necessary.
Refer to spark
plug
diagnosis
information
presented in Engine Elec-
trical
for an analysis of
plug
conditions.
2.
Clean serviceable spark plugs thoroughly, using
an abrasive-type cleaner.
File
the center electrode
flat.
3. Inspect
each
spark
plug
for make and
heat
range. All plugs must be of the
same
make and
number or
heat
range. (See section 6E. for correct
spark
plug
usage.)
4.
Adjust spark
plug
gaps
to
.035"
using a round
feeler gauge.
CAUTION:
Never bend the center electrode to
adjust
gap. Always adjust by bending ground or
side
electrode.
5. If available,
test
plugs
with
a spark
plug
tester.
6. Inspect spark
plug
hole
threads
and clean be-
fore
installing
plugs. Corrosion deposits can be re-
moved
with
a 14 mm. x 1.25 SAE spark
plug
tap
(available
through
local
jobbers) or by using a small
wire
brush in an electric
drill.
Use plenty of
grease
on
tap to catch any chips.
CAUTION:
Use extreme
care
when using tap to
prevent
cross
threading.
Also
crank engine
several
times to blow out any material dislodged
during
cleaning
operation.
7.
Install
spark plugs to engine
with
new
gaskets
and tighten to 25 lb. ft. torque.
Improper
Installation is one of the
greatest
single
causes
of unsatisfactory spark
plug
performance.
Improper
installation is the result of one or more of
the
following
practices:
•
Installation of plugs
with
insufficient
torque to
fully
seat
the gasket.
•
Installation of the plugs using excessive torque
which
changes
gap settings.
•
Installation of plugs on
dirty
gasket seal.
•
Installation of plugs to corroded spark
plug
hole
threads.
Failure
to
install
plugs properly
will
cause
them to
operate
at excessively
high
temperatures and result
in
reduced operating
life
under
mild
operation or
complete destruction under
severe
operation where
the intense
heat
cannot be dissipated rapidly enough.
Always
remove corrosion deposits in hole
threads
before
installing
plugs. When corrosion is
present
in
threads, normal torque is not sufficient to compress
the
plug
gasket and early failure
from
overheating
will
result.
Always
use a new gasket and wipe
seats
in head
clean. The gasket must be
fully
compressed on clean
seats
to complete
heat
transfer and provide a gas
tight
seal
in the cylinder. For this reason as
well
as
the necessity of maintaining correct
plug
gap, the use
of
correct torque Is extremely Important during
installation.
IGNITION
SYSTEM
SERVICE
AND
REPAIRS
1. Replace
brittle
or damaged spark
plug
wires.
Install
all wires to proper spark
plug.
Proper posi-
tioning
of spark
plug
wires in supports is important
on
V-8 engines to prevent cross-firing.
2.
Tighten all
Ignition
system connections.
3. Replace or repair any wires that are frayed,
loose or damaged.
4.
Remove distributor cap, clean cap and inspect
for
cracks, carbon tracks and burned or corroded
terminals.
Replace cap where
necessary.
5. Clean rotor and Inspect for
damage
or deteri-
oration.
Replace rotor where
necessary.
6. Check the distributor centrifugal
advance
mech-
anism by turning the distributor rotor as far as
possible, then releasing the rotor to see if the
springs return it to its
original
position. If the
rotor
does
not return readily, the distributor must
be disassembled and the
cause
of the trouble
corrected.
7. Check to see that the vacuum
advance
control
operates
freely by turning the movable breaker plate
to
see if the spring returns to its
original
position.
Any
stiffness in the operation of the spark control
will
affect the
ignition
timing.
Correct any inter-
ference or binding condition noted.
8. Examine distributor points and clean or replace
if
necessary.
To Next Page
Loading...
