check engine CHEVROLET CAMARO 1967 1.G Chassis Owner's Guide

BRAKES
5-31

POWER BRAKES

INDEX

General Description 5-31

Maintenance
and"
Adjustments 5-31

Inspection . ... 5_31

Lubrication 5-31

Bleeding Instructions . . . 5.31

Air Cleaner Service . . . , 5.31
Page

Component Replacement 5-31

Power Brake Cylinder ......* 5-31

Removal . . 5-31

Disassembly and Assembly See Overhaul Manual

Installation . . . . 5-31

GENERAL DESCRIPTION

The Power Brake Unit is a self-contained hydraulic

and vacuum unit, utilizing manifold vacuum and atmos-

phere pressure for its power.

This unit permits the use of a low brake pedal as well

as less pedal effort than is required with the conventional

(nonpower) hydraulic brake system. Only two external
line connections are necessary -
one
a vacuum connection

from manifold to check valve located on front shell; the

other, a hydraulic connection from the main cylinder

outlet directly into the hydraulic system. The unit is

mounted on the engine side of the fire wall and directly

connected to the brake pedal.

MAINTENANCE AND ADJUSTMENTS

INSPECTIONS

1.
Check vacuum line and vacuum line connections as

well as vacuum check valve in front shell of power

unit for possible vacuum loss.

2.
Inspect all hydraulic lines and connections at the

wheel cylinders and main cylinder for possible

hydraulic leaks.

3.
Check brake assemblies for scored drums, grease

or brake fluid on linings, worn or glazed linings,

and make necessary adjustments.

4.
Check brake fluid level in the hydraulic reser-

voirs.
The reservoirs should be filled to the levels

shown in Figure 8.

5. Check for loose mounting bolts at main cylinder and

at power section.

6. Check air cleaner filter in power piston extension

and replace filter if necessary.

7. Check brake pedal for binding and misalignment

between pedal
-and
push rod.

LUBRICATION

The power brake unit is lubricated at assembly and
needs no further lubrication other than maintaining

normal reservoir fluid level. The reservoir should be

filled as described in this section.

BLEEDING INSTRUCTIONS

The power system may be bled manually or with a

pressure bleeder as outlined in this section. Use only

GM
Supreme 11 Brake Fluid or equivalent. Do not use the

power assist while bleeding. The engine should not be

running and the vacuum reserve should be reduced to

zero by applying the brake several times before starting

the bleeding procedure.

AIR CLEANER SERVICE

Servicing of the air cleaner is recommended and the

element replaced when restriction becomes severe

enough to affect power brake response. At any other

time, if cleaning of the filter is felt necessary, it should

be shaken free of dirt or washed in soap and water and

thoroughly dried.

COMPONENT REPLACEMENT

POWER BRAKE CYLINDER

Removal

1.
Remove vacuum hose from vacuum check valve.

2.
Disconnect hydraulic lines at main cylinder.

Disconnect push rod at brake pedal assembly.

Remove nuts and lock washers securing power unit

to fire wall, and remove power unit from engine

compartment.
3.

4.

NOTE:
Chevy

to fire wall.
has a three stud attachment

Repair procedures for the power cylinder are outlined

in the Brake Section of the Overhaul Manual-for service
of the main cylinder refer to applicable portion of

"Standard Brakes" in this manual.

Installation

1.
Mount the power brake assembly in place and install

the attaching nuts and lock washers.

2.
Attach vacuum line to check valve.

3.
Secure hydraulic lines to main cylinder.

4.
Attach push rod to brake pedal assembly, and check

operation of stop light.

5. Bleed brakes as outlined in this section.

CAUTION: After replacing the unit on the vehi-

cle,
start the engine and allow vacuum to build

up before applying the brake.

CHEVROLET CHASSIS SERVICE

SECTION 6

ENGINE

CONTENTS
OF
THIS SECTION

Page

Engine Tune Up
6-1
Torque Sequence

Engine Mechanical
(In
Line)
6-12
Special Tools
. .

Engine Mechanical (V8)
6-24
Page

6-39

6-40

ENGINE TUNE UP

INDEX

Page

General Description
. 6-1

Mechanical Checks and Adjustments
6-1

Spark Plug Removal
6-1

Test Compression
6-1

Service and Install Spark Plugs
6-2

Service Ignition System
6-3

Service Battery
and
Battery Cables
6-5

Service Delcotron
and
Regulator
6-5

Service
Fan
Belt
6-5

Service Manifold Heat Valve
6-5

Tighten Manifold
6-5

Service Fuel Lines
and
Fuel Filter ..........
6-6

Service Cooling System
6-6

Check and Adjust Accelerator Linkage
6-6

Service Crankcase Ventilation
6-6

Service
Air
Injection Reactor System
6-6

Choke Adjustment
6-7
Page

Instrument Cheek-Out
6-7

Instrument Hook-Up.
. 6*7

Check and Adjust Dwell
6-7

Check Dwell Variation
6-7

Check and Adjust Timing
6-8

Adjust Idle Speed
and
Mixture
6-8

Additional Checks and Adjustments
. 6-8

Testing Crankcase Ventilation Valve
. 6-8

Testing Cranking Voltage
6-8

Cylinder Balance Test
. 6-8

Battery
6-8

Ignition
; 6-8

Carburetor
6-11

Fuel Pump
6-11

Cooling System
. 6-11

Cylinder Head Torque and Valve Adjustment
..... 6-11

GENERAL DESCRIPTION

The engine tune up
is
important
to the
modern automo-

tive engine with
its
vastly improved power and perform-

ance.
The
higher compression ratios, improved electri-

cal systems
and
other advances
in
design, make today1 s

engines more sensitive
and
have
a
decided effect
on

power, performance and fuel consumption.

It
is
seldom advisable
to
attempt
a
tune up
by
correc-

tion
of one or two
items only. Time will normally
be

saved
and
more lasting results assured
if the
technician

will follow
a
definite
and
thorough procedure
of
analysis

and correction
of all
items affecting power, performance

and economy.

The tune
up
will
be
performed
in
two parts.
The
first

part will consist
of
visual and mechanical checks and
ad-

justments;
the
second part will consist
of
an instrument

checkout that
can be
performed with
any one of the
units
of service equipment available
for
this purpose. Always

follow
the
instructions provided
by the
manufacturer
of

the particular equipment
to be
used.

Additional checks
and
adjustments
are
included
in the

latter part
of
this section
for use as
required. Many
of

these operations
can be
used
to
isolate and correct trou-

ble located during
the
tune up. Where conditions
are
UB-

covered requiring major corrective action, refer
to the

appropriate section
of
this manual
or the
Passenger

Chassis Overhaul Manual
for
detailed service informa-

tion.

Typical illustrations
and
procedures
are
used except

where specific illustrations
or
procedures
are
necessary

to clarify
the
operation. Illustrations showing bench
op-

erations
are
used
for
clarification however
all
operations

can
be
performed
on the
vehicle.

MECHANICAL CHECKS
AND
ADJUSTMENTS

Spark Plug Removal

Remove any foreign matter from around spark plugs
by

blowing
out
with compressed
air,
then disconnect wires

and remove plugs.

Test Compression
(Fig. 1)

The compression check
is
important because
an
engine

with
low or
uneven compression cannot
be
tuned success-
fully.
It is
essential that improper compression
be cor-

rected before proceeding with
the
engine tune
up.

1.
Remove
air
cleaner
and
block throttle
and
choke
in

wide open position.

2.
Hook
up
starter remote control cable
and
insert

compression gauge firmly
in
spark plug port.

CAUTION: Whenever
the
engine
is
cranked

CHEVROLET
C*
IS SERVICE MANUAL

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
6-5

Service Battery and Battery Cables

1.
Measure the specific gravity of the electrolyte in

each cell (fig. 6). If it is below 1.230 (corrected to

80°F.) recharge with a slow rate charger, or if de-

sired, further check battery.

2.
Connect a voltmeter across the battery terminals and

measure the terminal voltage of the battery during

cranking (disconnect the coil primary lead at the

negative terminal during this check to prevent engine

from firing). If the terminal voltage is less than 9.0

volts at room temperature, approximately 80°

±
20°
F.,
the battery should be further checked. See

Section 6Y for further tests.

3.
Inspect for signs of corrosion on battery, cables and

surrounding area, loose or broken carriers, cracked

or bulged cases,- dirt and acid, electrolyte leakage

and low electrolyte level. !Fill cells to proper level

with distilled water or water passed through a

"demineralizer".

The top of the battery should be clean and the bat-

tery hold-down bolts properly tightened. Particular

care should be taken to see that the top of the battery

is kept clean of acid film and dirt. When cleaning

batteries, wash first with a dilute ammonia or soda

solution to neutralize any acid present and then flush

off with clean water. Keep vent plugs tight so that

the neutralizing solution does not enter the cell. The

hold-down bolts should be kept tight enough to prevent

the battery from shaking around in its holder, but

they should not be tightened to the point where the

battery case will be placed under a severe strain.

To insure good contact, the battery cables should

be tight on the battery posts. Oil battery terminal

felt washer. If the battery posts or cable terminals
are corroded, the cables should be cleaned separately

with a soda solution and wire brush. After cleaning

and before installing clamps, apply a thin coating of

petrolatum to the posts and cable clamps to help

retard corrosion.

If the battery has remained undercharged, check

for loose or defective fan belt, defective Delcotron,

high resistance in the charging circuit, oxidized

regulator contact points, or a low voltage setting.

If the battery has been using too much water, the

voltage output
is-
too high.

Service Deicotron and Regulator

The Delcotron and regulator tests during tune up con-

sist of the above battery tests; the condition of the battery

indicating further tests and adjustments as outlined in

Section 6Y.

Service Belts (Fig. 7)

Inspect belt condition.

Check and adjust if necessary for correct tension of

belt, as follows:

• Using a strand tension gauge, check the belt tension.

• Adjust belt until the specified tension is reached.

(See Tune Up Chart.)

Service Manifold Heat Valve (Figs. 8 or 9)

Check manifold heat control valve for freedom of oper-

ation. If shaft is sticking, free it up with GM Manifold

Heat Control Solvent or its equivalent.

NOTE: Tap shaft end to end to help free it up.

Tighten Manifold

Tighten intake manifold bolts to specifications in the

FLAME

ARRESTOR
FLAME

ARRESTOR

NON-VENTED\

CAP
V\ VALVE

CLOSED
POSITIVE (283 & 327)

POSITIVE
(IN LINE)

POSITIVE
(327)

POSITIVE
(396 & 427)

Fig.
10 -
Crank case
Ventilation Systems

CHEVROLET CHASSIS SERVICE MANUAL

ENGINE 6-6

CHOKE VALVE

COMPLETELY

CLOSED

PULL UPWARD ON

ROD TO END OF

TRAVEL

BEND ROD

TO ADJUST
ROD IN BOTTOM

OF SLOT

BOTTOM OF

ROD SHOULD

EVENWITH

TOP OF

HOLE
CHOKE VALVE

CLOSED

BOTTOM OF

ROD SHOULD

BE EVEN WITH

TOP OF HOLE

TOP OF ROD

SHOULD BE EVEN

WITH BOTTOM

OF HOLE (CHOKE

CLOSED)

^..BEND ROD TO

ADJUST

_PULL DOWNWARD

ON ROD TO CON-

TACT STOP

L6 (TYPICAL)

V8 327-275 HP

V8 350-295 HP
BEND ROI

TO ADJUST

PULL UPWARD ON

ROD TO CONTACT

STOP ON BRACKET

ALL V8 (EXCEPT 327-275 HP

AND 350-295 HP)

Fig.
11 - Remote Choke Adjustment

sequence outlined on Torque Sequence Chart. A slight

leak at the intake manifold destroys engine performance

and economy.

Service Fuel Lines and Fuel Filter

1.
Inspect fuel lines for kinks, bends or leaks and cor-

rect any defects found, • • •

2.
Inspect filter and replace if plugged.

NOTE:
If a complaint of poor high speed per-

formance exists on the vehicle, fuel pump tests

described in Section 6M should be performed.

Service Cooling System

1.
Inspect cooling system for leaks, weak hoses, loose

hose clamps and correct coolant level, and service

as required.

NOTE:
A cooling system pressure test, as de-

scribed in "Additional Checks and Adjustments"

in this section, may be performed to detect

internal or external leaks within the cooling

system.

Check and Adjust Accelerator Linkage

1.
Disconnect accelerator rod at carburetor throttle

lever.

2.
Hold carburetor throttle lever in wide position.

3.
Pull accelerator rod to wide open position. (On ve-

hicles equipped with automatic transmission, pull

through detent).

4.
Adjust accelerator rod to freely enter hole in carbu-

retor throttle lever.'

NOTE:
Accelerator linkage is outlined in de-

tail in Section 6M.
5. Connect accelerator rod at throttle lever.

Service Crankcase Ventilation (Fig. 10}

All engines have either "Positive" or "Closed Positive"

ventilation systems utilizing manifold vacuum to draw

fumes and contaminating vapors into the combustion

chamber where they are burned. Since it affects every

part of the engine, crankcase ventilation is an important

function and should be understood and serviced properly.

In both "Positive" and "Closed Positive" ventilation,

air is drawn through the engine, (through a regulating

valve) into the manifold, drawing' crankcase vapors and

fumes with it to be burned. "Positive" ventilation uses a

vented-meshed cap for clean air intake to the engine,

while . "Closed Positive" ventilation system draws the

clean air from the carburetor air cleaner and has a

nonvented oil filler cap.

1.
Ventilation valve may be checked as outlined under

"Additional Checks and Adjustments".

2.
Inspect for deteriorated or plugged hoses.

3.
Inspect all hose connections.

4.
On closed positive ventilation systems, remove flame

arrestor and wash in solvent then dry with com-

pressed air.

Service Air Injection Reactor System

Inspect air injection reactor system for evidence of

leaks,
deteriorated hoses, cracked air manifolds or tubes

and loose hose clamps. Inspect air injection pump belt

condition and tension. Make all necessary repairs as

outlined in "Section 6T".

Because of the relationship between "Engine Tune Up"

and "Unburned Exhaust Gases", the condition of Engine

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