ENGINE 6-2
remotely at the starter, with a special jumper
cable or other means, the primary distributor
lead must be disconnected from the negative
post on the coil and the ignition switch must be
in the "ON" position. Failure to do this will
result in a damaged grounding circuit in the
ignition switch.
3.
Crank engine through at least four compression
strokes to obtain highest possible reading.
4.
Check and record compression of each cylinder.
5.
If one or more cylinders read low tor uneven, inject
about a tablespoon of engine oil on top of pistons
in low reading cylinders (through spark plug
port).
Crank engine several times and recheck
compression.
• If compression comes up but does not necessarily
reach normal, rings are worn.
• If compression does not improve, valves are
burnt, sticking or not seating properly.
• If two adjacent cylinders indicate low compres-
sion and injecting oil does not increase compres-
sion, the cause may be a head gasket leak between
the cylinders. Engine coolant and/or oil in cylin-
ders could result from this defect.
NOTE: If a weak cylinder cannot be located
with the compression check, see "Cylinder Bal-
ance Test" under "Additional Checks and Adjust-
ments" in this section.
Service and Install Spark Plugs (Fig. 2)
1.
Inspect each plug individually for badly worn elec-
trodes,
glazed, broken or blistered porcelains and
replace plugs where necessary. Refer to spark plug
diagnosis information presented in Section 6Y for an
analysis of plug conditions.
2.
Clean serviceable spark plugs thoroughly, using an
abrasive-type cleaner such as sand blast. 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.
4.
Adjust spark plug gaps to specifications using a
round feeler gauge.
PORCELAIN
INSULATOR
INSULATOR CRACKS
OFTEN OCCUR HERE
CENTER ELECTRODE
[FILE FLAT WHEN
ADJUSTING GAP-
[DO NOT BEND!
(PROPER GAP)
(BEND TO ADJUST GAP)
CAUTION:
adjust gap.
Fig.
2 - Spark Plug Detail
Never bend the center electrode to
Always adjust by bending ground or
side electrode.
If available, test plugs with a spark plug tester.
Inspect spark plug hole threads and clean before in-
stalling plugs. Corrosion deposits can be removed
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 grease on tap to catch
chips.)
ADJUST DWELL
ANGLE SETTING OR
POINT OPENING
Fig.
1 - Checking Compression
Fig.
3 - Distributor (In Line)
CHEVROLET CHASSIS SERVICE MANUAL
ENGINE
6-3
(ROUND) Y~~fll^H
CENTRIFUGAL
A ^k
ADVANCE--jflgKpl
MECHANISM
UB|
CAM
KSK^2
LUBRICATOR
VlSMi
REPLACEMENT
^BK
-^ADJUST
SQUARELY
AND
JUST
TOUCHING
LOBE
OF
CAM
/ROTOR
HBB
__
I^BH^F
?
(SOUARE)
^K^ I /—
CAM
jKft^J / LUBRICATOR
H^T^
CAUTION!
QV NEVER
OIL
•L-^
CAM LUBRICATOR-
REPLACE
WICK
WHEN
NECESSARY
LATERAL
MISALIGNMENT
PROPER
LATERAL ALIGNMENT
Fig.
4- Distributor (V8)
CAUTION: Use extreme care
-when
using tap to
prevent cross threading. Also crank engine sev-
eral times to blow out any material dislodged
during cleaning operation.
7. Install spark plugs with new gaskets and torque to
specifications.
NOTE:
The following are some of the
greatest causes of unsatisfactory spark plug
performance.
•
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 into corroded spark plug hole
threads.
8^ Connect spark plug wiring.
Service
Ignition System
1.
Remove distributor cap, clean cap and inspect for
cracks, carbon tracks and burned or corroded ter-
minals. Replace cap where necessary.
2.
Clean rotor and inspect for damage or deterioration.
Replace rotor where necessary.
3.
Replace brittle, oil soaked or damaged spark plug
wires.
Install all wires to proper spark plug. Proper
positioning of spark plug wires in supports is impor-
tant to prevent cross-firing.
4.
Tighten all ignition system connections.
5. Replace or repair any wires that are frayed, loose or
damaged.
Us
CORRECT
LATERAL MISALIGNMENT BY
j BENDING
FIXED CONTACT SUPPORT
[NEVER
BEND BREAKER LEVER
Fig.
5 - Point Alignment
Magnetic
Pulse(Breakerless)
Distributor
There are no moving parts in the ignition pulse ampli-
fier, and the distributor shaft and bushings have perma-
nent type lubrication, therefore no periodic maintenance
is required for the magnetic pulse ignition system. Refer
to Section 6Y for an analysis of problems and/or repair
procedures encountered on the Transistorized (Magnetic
Pulse) ignition system.
Standard
(Breaker Point) Distributor
(Figs.
3 or 4)
1.
Check the distributor centrifugal advance mechanism
by turning the distributor rotor in a clockwise direc-
tion as far as possible, then releasing the rotor to
see if the springs return it to its retarded position.
If the rotor does not return readily, the distributor
must be disassembled and the cause of the trouble
corrected.
2.
Check to see that the vacuum spark control operates
freely by turning the movable breaker plate counter-
clockwise to see if the spring returns to its retarded
position. Any stiffness in the operation of the spark
control will affect the ignition timing. Correct any
interference or binding condition noted.
3.
Examine distributor points and clean or replace if
riecessary.
DO
NOT SUCK
IN
TOO MUCH
ELECTROLYTE
TAKE
READING
AT
EYE LEVEL
Fig.
6 - Testing Specific Gravity of Battery
CHEVROtET
CHASSIS SERVICE MANUAL
ENGINE 6-4
• Contact points with an overall gray color and only
slight roughness or pitting need not be replaced.
• Dirty points should be cleaned with a clean point
file.
Use only a few strokes of a clean, fine-cut con-
tact file. The file should not be used on other
metals and should not be allowed to become
greasy or dirty. Never use emery cloth or sand-
paper to clean contact points since particles will
embed and cause arcing and rapid burning of
points. Do not attempt to remove all roughness
nor dress the point surfaces down smooth.
Merely remove scale or dirt.
• Clean cam lobe with cleaning solvent, lubricate
cam lobe with "Delco Remy Cam and Ball Bearing
Lubricant" or its equivalent and rotate cam lubri-
cator wick 1/2 turn.
• Replace points that are burned or badly pitted.
NOTE: Where prematurely burned or badly
pitted points are encountered, the ignition sys-
tem and engine should be checked to determine
the cause of trouble so it can be eliminated.
Unless the condition causing point burning or
pitting is corrected, new points will provide no .
better service than the old points. Refer to
Section 6Y for an analysis of point burning or
pitting.
• Check point alignment (fig. 5) then, adjust distri-
. butor contact point gap to .019" (new points) or
.016"
(used points). Breaker arm rubbing block
must be on high point of lobe during adjustment.
NOTE: If contact points have been in service,
they should be cleaned with a point file before
adjusting with a feeler gauge.
• Check distributor point spring tension (contact
Fig. 8 - Manifold Heat Control Valve (In Line)
point pressure) with a spring gauge hooked to
breaker lever at the contact and pull exerted at 90
degrees to the breaker lever. The points should
be closed (cam follower between lobes) and the
reading taken just as the points separate. Spring
tension should be 19-23 ounces. If not within
limits,
replace.
Excessive point pressure" will cause excessive
wear on the points, cam and rubber block. Weak
point pressure permits bouncing or chattering,
resulting in arcing and burning of the points and
an ignition miss at high speed.
4.
Install rotor and distributor cap. Press all wires
firmly into cap towers.
Fig. 7 - Checking Fan Belt Tension
Fig. 9 - Manifold Heat Control Valve (V8)
CHEVROLET CHASSIS SERVICE MANUAL
ENGINE 6-7
Tune Up should be checked whenever the Air Injection
Reactor System seems to be malfunctioning. Particular
care should be taken in checking items that affect fuel-air
ratio such as the crankcase ventilation system, the car-
buretor and the carburetor air cleaner. Carburetors and
distributors for engines with the Air Injection Reactor
System are designed, particularly, for these engines;
therefore, they must not be interchanged with or replaced
by a carburetor or distributor designed for an engine
without the Air Injection Reactor System.
Choke Adjustment (Fig. 11)
With Remote Choke
1.
Remove air cleaner and check to see that choke
valve and rod move freely.
2.
Disconnect choke r*od at choke lever.
Check choke adjustment as follows:
On all except 275 hp 327 cu. in. engines, hold
choke valve closed and pull rod up against stop. The
top of choke rod end should be 1/2 - 1 rod diameter
4.
5.
above top of hole in choke valve lever.
On 275 hp 327 cu. in. engines, hold choke valve
closed and push rod down against stop on thermostat
bracket. The top of the choke rod should be 1/2 - 1
rod diameter below the top of the hole in the choke
lever.
If necessary, adjust rod length by bending rod at off-
set. (Bend must be such that rod enters choke lever
hole freely and squarely.)
Connect rod at choke lever and install air cleaner.
3.
With Manual
Choke
1.
Remove air cleaner.
2.
Push hand choke knob in to within 1/8" of instrument
panel.
3.
Loosen choke cable at carburetor bracket and adjust
cable through the clip until the choke valve is wide
open.
4.
Tighten cable clamp at carburetor bracket and check
operation of choke valve to ensure full closed and
wide open positions.
INSTRUMENT CHECK-OUT
Instrument Hook Up
Connect vacuum gauge, dwell meter, tachometer and
timing light as recommended by the manufacturer of the
equipment being used.
Check and Adjust Dwell
1.
Start engine then ch^ck ignition dwell.
.2.
If dwell is not within specifications, adjust dwell as
follows:
V8 ENGINES
• With engine running at idle, raise the adjustment
screw window-and insert an Allen wrench in the
socket of the adjusting screw (fig. 12).
• Turn the adjusting screw as required until a dwell
reading of 30° is obtained. A 2° variation is al-
lowable for wear.
• Close access cover fully to prevent the entry of
dirt into the distributor.
NOTE: If a dwell meter is not available, turn
adjusting screw clockwise until engine starts to
misfire, then turn screw one-half turn in the op-
posite direction to complete adjustment.
IN LINE ENGINES
• Remove distributor cap and recheck point setting.
If dwell is still not within specifications check the
distributor as outlined in Section 6Y.
Check Dwell Variation
Slowly accelerate engine to 1500 rpm and note dwell
reading. Return engine to idle and note dwell reading. If
dwell variation exceeds specifications, check for worn
distributor shaft, worn distributor shaft bushing or loose
breaker plate.
WINDOW
"HEX" TYPE
WRENCH
Fig.
12 - Setting Point Dwell (V8)
Fig.
13 - Ignition Timing Marks
CHEVROLET CHASSIS SERVICE MANUAL
ENGINE
6-8
Check
and
Adjust Ignition Timing
(Fig. 13)
1.
Disconnect
the
distributor spark advance hose
and
plug
the
vacuum source opening.
2.
Start engine
and run at
idle speed
(see
tune
up
chart).
3.
Aim
timing light
at
timing
tab.
NOTE:
- The
markings
on the
tabs
are in 2°
increments
(the
greatest number
of
markings
on
the
"A"
side
of the "O"). the "O"
markings
is
TDC
of
#1 cylinder
and all
BTDC settings fall
on
the
"A"
(advance) side
of "O".
4.
Adjust
the
timing
by
loosening
the
distributor clamp
and
,
rotating
the
distributor body
as
required, then
tighten
the
clamp.
5.
Stop engine
and
remove timing light
and
reconnect
the spark advance hose.
Adjust Idle Speed
and
Mixture
(Fig. 14)
(Except when
equipped with
Air
Injection Reactor System)
1.
As a
preliminary adjustment, turn idle mixture
screws lightly
to
seat
and
back
out 2
turns.
CAUTION:
Do not
turn idle mixture screw
tightly against seat
or
damage
may
result.
2.
With engine running
at
operating temperature (choke
wide open) adjust idle speed screw
to
bring idle
speed
to
specified
rpm
(automatic transmission
in
drive, manual transmission
in
neutral).
3.
Adjust idle mixture screw
to
obtain highest steady
idle speed
(1/4
turn
out
from lean roll).
4.
Repeat Steps
2 and 3 as
needed
for
final adjustment.
5.
Shut down
the
engine, remove gauges
and
install
air
cleaner.
Adjust Idle Speed
and
Mixture
(Fig. 14)
(With
Air
Injection Reactor System)
The recommended adjustment procedure
for Air
Injec-
tion Reactor System equipped engines
is as
follows:
1.
As a
preliminary adjustment, turn idle mixture
screws lightly
to
seat
and
than back
out 3
turns.
CAUTION:
Do not
turn idle mixture screw
tightly against seat
or
damage
may
result.
2.
With engine running
at
operating temperature, choke
wide open,
and
parking brake applied, adjust idle
specified idle speed (automatic
"drive"-manual transmission
in
to
in
screw
transmission
"neutral").
;3.
Adjust idle mixture screw (turn
in) to
"lean roll"
position; then turn screw
out 1/4
turn
(1/4
turn rich
from "lean roll").
The
definition
of
"lean roll" point
is
a 20 to 30 rpm
drop
in
engine speed, obtained
by
leaning
the
idle mixture.
4.
Repeat Steps
2 and 3 as
needed
for
final adjustments.
ADDITIONAL CHECKS
AND
ADJUSTMENTS
Testing Crankcase Ventilation Valve
(Fig. 15) 0
1.
Connect tachometer
and
vacuum gauge
as for
idle
speed
and
mixture adjustment.
2.
Set
parking brake, start engine
and
adjust idle speed
and mixture.
3.
Disconnect ventilation hose
at
valve, block opening
of
valve
and
read engine
rpm
change.
4.
A
change
of
less than
50 rpm
indicates
a
plugged
ventilation valve
-
replace
the
valve.
Cylinder Balance Test
(Fig. 16)
It
is
often difficult
to
locate
a
weak cylinder.
A com-
pression test,
for
example, will
not
locate
a
leaky intake
manifold,
a
valve
not
opening properly
due to a
worn
camshaft,
or a
defective spark plug.
With
the
cylinder balance test,
the
power output
of one
cylinder
may be
checked against another, using
a set of
grounding leads. When
the
power output
of
each cylinder
is
not
equal,
the
engine will lose power
and run
roughly.
Perform
a
cylinder balance test
as
follows:
1.
Connect
the
tachometer
and
vacuum gauge.
2.
Start engine
and run at 1500 rpm.
3.
Ground large clip
of
grounding leads
and
connect
in-
dividual leads
to all
spark plugs except
the
pair being
tested.
Divide
the
firing order
in
half
and
arrange
one
half
over
the
other.
The
cylinders
to be
tested together
ap-
pear
one
over
the
other.
L4 Firing Order
V8 Firing Order
1-8-4-3-6-5-7-2
1-6, 8-5, 4-7, 3-2
1-3-4-2
= 1-3
4-2
L6 Firing Order
1-5-3-6-2-4
=
=
1-4. 3-2
1-5-3
6-2-4
1-6, 5-2, 3-4
1-8-4-3
6-5-7-2
4.
Operate engine
on
each pair
of
cylinders
in
turn
and
note engine
rpm and
manifold vacuum
for
each pair.
A variation
of
more than
1
inch
of
vacuum
or 40 rpm
between pairs
of
cylinders being tested indicates that
the cylinders
are off
balance.
Battery
The battery should
be
checked with special testing
equipment
and to the
equipment manufacturers specifica-
tions.
See
Section 6Y
for
complete information
on
battery
tests.
Ignition
The following additional ignition checks
may be
made
with
any of
several pieces
of
equipment available
for un-
covering
the
source
of
engine difficulties.
The
specific
operating instructions
of the
equipment manufacturer
should
be
followed:
Cranking voltage
Ignition switch
Distributor resistance
Secondary resistance
Ignition output
and
secondary leakage
Cranking Voltage
(Fig. 17)
1.
Disconnect coil primary lead
at the
coil negative
terminal
to
prevent engine from firing during
cranking.
2.
Connect voltmeter between primary terminal
of coi|
(resistance wire side)
and
ground.
3.
Operate starting motor.
CHEVROLET CHASSIS SERVICE MANUAL
ENGINE 6-10
Fig.
15 - Crank case Ventilation Valve
a. If voltage is 9 volts or more and cranking speed
is satisfactory, the battery, starter, cables,
starter switch and ignition circuit to coil (by-
passing resistance wire) are in good condition.
b.
If below 9 volts, check circuit until difficulty is
located.
Meter reading below specification—Weak bat-
tery; defective cables, connections, switch or
starter; defective ignition circuit to coil.
Cranking speed below normal--Excessive re-
sistance in cables or starting motor; excessive
mechanical drag in engine.
Uneven cranking speed—Uneven compression,
defective starter or starter drive.
Ignition Switch
With voltmeter connected as described for the Cranking
Voltage Test, turn ignition switch to ON. Voltage should
drop to 5 to 7 volts as current is now passing through
high resistance wire connected between ignition switch
and (+) positive terminal of coil. If battery voltage of
12 volts is obtained, the starter solenoid is by-passing
the high resistance wire connected between ignition
switch and (+) positive terminal of coil, thus the starter
solenoid is not functioning properly to bypass the ignition
resistance wire or the ignition circuit is incorrectly
wired.
Distributor Resistance
Use equipment as directed by manufacturer.
Excessive
(t n ti ft
Fig.
16 - Cylinder Balance Test
Fig.
17 - Testing Cranking Voltage
resistance in primary circuit must be eliminated before
continuing with test procedure.
Secondary Resistance
Use equipment as dire6ted by manufacturer.
• Uniform "normal readings" as specified by manu-
facturer indicate all secondary circuit components
are in good condition.
• If all readings are "below normal," check for cor-
roded coil tower terminal, poorly connected or
broken coil wire, center cap electrode or rotor tip
burned, or an open secondary in coil.
• If readings are "higher than normal" at two or more
plugs adjacent in firing order, cross firing is oc-
curring in distributor cap or between spark plug ca-
bles concerned.
• If meter reads off scale to left, the coil polarity is
reversed. Check for reversed coil primary wires,
wrong coil or reversed vehicle battery connections.
Ignition Output and Secondary Leakage
Use equipment as directed by manufacturer.
• GOOD readings indicate both ignition output and
secondary insulation are good.
• If all readings are BAD or if ignition test calibrator
cannot be adjusted to Set Line, check for high re-
sistance in primary circuit, defective distributor
points, coil or condenser.
e If readings are BAD when certain plug wires are
lifted off, check for cracks or carbon tracks in dis-
tributor cap or defective insulation on those plug
wires being lifted off.
CHEVROLET CHASSIS SERVICE MANUAL
ENGINE 6-16
5.
Adjust ignition timing and carburetor idle speed and
mixture.
VALVE STEM OIL SEAL AND/OR VALVE SPRING
Replacement
1.
Remove rocker arm cover as outlined.
2.
Remove spark plug, rocker arm and push rod on the
cylinder(s) to be serviced.
3.
Apply compressed air to the spark plug hole to hold
the valves in place.
NOTE: A tool to apply air to the cylinder is
available through local jobbers or may be manu-
factured. In manufacturing this Tool a AC-46N
Spark Plug or its equivalent is recommended.
This will make the Tool universal for all
Chevrolet engines. Chisel the spark plug as
shown, then drive the porcelain out of the plug
by tapping the center electrode against a hard
block. Using a 3/8" pipe tap, cut threads in the
remaining portion of the spark ^>lug and assem-
ble as shown (fig. 3L).
4.
Using Tool J-5892 to compress the valve spring, re-
move the valve locks, valve cap, valve shield and
valve spring and damper (fig. 4L).
5.
Remove the valve stem oil seal.
6. To replace, set the valve spring and damper, valve
shield and valve cap in place. The close coiled end
of the spring is installed against the cylinder head.
Compress the spring with
Too^
J-5892 and install oil
seal in the lower groove of the stem, making sure the
seal'is flat and not twisted.
NOTE: A light coat of oil on the seal will help
prevent twisting.
7.
Install the valve locks and release the compressor
tool, making sure the locks seat properly in the
upper groove of the valve stem.
NOTE: Grease may be used to hold the locks
in place while releasing the compressor tool.
8. Install spark plug, using a new gasket, and torque to
specifications.
9. Install and adjust valve mechanism as outlined.
CYLINDER HEAD ASSEMBLY
Removal
1.
Remove manifold assembly as. outlined.
2.
Remove valve mechanism as outlined.
3.
Drain cooling system (block).
4.
Remove fuel and vacuum line from retaining clip at
water outlet then disconnect wires from temperature
sending units.
5.
Disconnect upper radiator hose at water outlet hous-
ing and battery ground strap at cylinder head.
6. Remove coil (L6 engines only).
7.
Remove cylinder head bolts, cylinder head and gas-
ket. Place cylinder head on two blocks of wood to
prevent damage.
Installation
CAUTION: The gasket surfaces on both the
head and the block must be clean of any foreign
matter and free of nicks or heavy scratches.
Cylinder bolt threads in the block and threads
on the cylinder head bolt must be cleaned. (Dirt
will affect bolt torque.) Do not use gasket sealer
on composition steel asbestos gasket.
Fig. 3L -
AIF
Adapter Tool
1.
Place the gasket in position over the dowel pins with
the bead up.
2.
Carefully guide cylinder head into place over dowel
pins and gasket.
3.
Coat threads of cylinder head bolts with sealing com-
pound and install finger tight.
4.
Tighten cylinder head bolts a little at a time in the
sequence shown on the torque sequence chart until
the specified torque is reached.
5.
Install coil (if removed).
6. Connect upper radiator hose and engine ground strap.
7.
Connect temperature sending unit wires and install
fuel and vacuum lines in clip at water outlet.
8. Fill cooling system.
•
9. Install manifold assembly as outlined.
10.
Install and adjust valve mechanism as outlined.
Fig.
4L
- Compressing Valve Spring
CHEVROLET CHASSIS SERVICE MANUAL
ENGINE 6-21
CAUTION: Support cover
•
at sealing area.
(Tool J-971 may be used as support.)
Without Cover
Removal
1.
With crankshaft pulley and nub or torsional damper
removed, pry old seal out of cover from the front
with a large screw driver, being careful not to dam-
age the seal surface on the cover.
2.
Install new seal so that open end of seal is toward the
inside of cover and drive it into position with Tool
J-8340 (fig. 13L).
CAMSHAFT
Measuring Lobe Lift
NOTE: Procedure is similar to that used for
checking valve timing.. If improper valve
operation is indicated, measure the lift of each
push rod in consecutive order and record the
readings.
1.
Remove valve mechanism as outlined.
2.
Position indicator with ball socket adapter on push
rod (fig. 14L).
3.
Rotate the crankshaft slowly in the direction of rota-
tion until the lifter is on the heel of the cam lobe.
At this point, the push rod will be in its lowest
position.
4.
Set dial indicator on zero, then rotate the crankshaft
slowly, or attach an auxiliary starter switch and
"bump" the engine over, until the push rod is in the
fully raised position.
CAUTION: The primary distributor lead must
be disconnected from the negative post on the
coil and the ignition switch must be in the ON
position. Failure to do this will result in a
damaged grounding circuit in the ignition switch.
Fig.
15L - Timing Gear Marks
5.
Compare the total lift recorded from the dial indica-
tor with specifications.
6. Continue to rotate the crankshaft until the indicator
reads zero. This will be a check on the accuracy of
the original indicator reading.
7.
If camshaft readings for all lobes are within specifi-
cations, remove dial indicator assembly.
8. Install and adjust valve mechanism as outlined.
Removal
1.
Remove valve lifters as outlined,
2.
Remove crankcase front cover as outlined.
3.
Remove radiator as outlined in Section 13.
4.
Remove grille as outlined in Section 13.
5.
Remove fuel pump as outlined in Section 6M.
6. Align timing gear marks then remove the two cam-
shaft thrust plate bolts by working through holes in
Fig.
ML - Measuring Camshaft Lobe Lift
Fig.
16L - Checking Camshaft Gear Runout
CHEVROLET CHASSIS SERVICE MANUAL