spark plugs OPEL GT-R 1973 User Guide

TUNE-UP
ALL MODELS
CONTENTS
Subject
DESCRIPTION AND OPERATION:
Purpose of a Tune-Up. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . .DIAGNOSIS: (Not Applicable)
MAINTENANCE AND ADJUSTMENTS:
EngineTune-UpMechanicalOperations. . . . . . . . . . . . . . . . . . . .
EngineTune-UpInstrumentChecks. . . . . . . . . . . . . . . . . . . . . . . . . . . .MAJOR REPAIR: (Not Applicable)
SPECIFICATIONS:
Tune-Uo Soecifications and Adjustments
. . . . . . . . . . . . . . . .Page No.6G-65
6G-6566-6766-68
DESCRIPTION AND OPERATION
PURPOSE OF TUNE-UP
The purpose of an engine tune-up is to restore powerand performance that may have been lost through,
loss of adjustment, wear, corrosion, or deterioration
of one or more parts or units. In the normal operat-
ion of an engine, these changes take place gradually
at quite a number of points so that it is seldom advis-able to attempt an improvement in performance by
correcting one or two items only. Time will be savedand more lasting results will be assured by following
a definite and thorough procedure of analysis and
correction of all items affecting power and perform-
ance. Because of Federal laws, limiting exhaust emis-sions, it is even more important that the engines
tune-up is done accurately, using the specifications
listed and the tune-up sticker found in each engine
compartment.
Economical, trouble free operation can better be as-sured if a complete tune-up is performed at first 4
months or
6,ooO miles of operation - then at 12
month or 12,000 mile intervals.
The parts or units which affect power and perform-
ance may be divided, into three groups (1) compres-sion, (2) ignition and (3) carburetion. The tune-up
procedure should cover these groups in the order
given. While the items affecting compression and
ignition may be handled according to individual
preference, correction of items in the carburetiongroup should not be attemplcu
ulllll all items in
compression and ignition have been satisfactorily
corrected.
MAINTENANCE AND ADJUSTMENTS
ENGINE TUNE-UP OPERATIONS
CompressionTo make sure hydrocarbon and carbon monoxide
emissions will be within limits, it is very important
that the adjustments be followed exactly.
The suggested procedure for engine tune-up is as
follows:1. Remove all spark plugs.
2. Position throttle and choke valve in full open posi-tion.
3. Connect jumper wire between distributor terminalof coil and ground on engine to avoid high tension
sparking while cranking engine.
4. Hook up starter remote control cable and turn
ignition switch to “on” position.
5. Firmly insert compression gage in spark plug port.Crank engine to obtain highest possible reading.

6G- 661973 OPEL SERVICE MANUAL
6. Check compression of each cylinder. Repeat
compression check and record highest reading ob-
tained on each cylinder during the two pressurechecks.The recorded compression pressures are to be con-
sidered normal if the lowest reading cylinder is more
than 75 percent of the highest reading cylinder. See
the following example and the “Compression Pres-
sure Limit Chart.” See Figure
6G-2.Seventy-five percent of 140 (highest) is 105. Thus,
cylinder No. 4 is less than 75 percent of No. 3. This
condition, accompanied by low speed missing, indi-
cates an improperly seated valve or worn or broken
piston ring. See Figure 6G-1.
23
I
SO-1Figure 6G-1 Example of Compression Check
7. If one or more cylinders read low, inject about a
tablespoon of engine oil on top of pistons in low
reading cylinders through spark plug port. Repeat
compression check on these cylinders.
a: If compression improves considerably, rings are
lV0*tl.b. If compression does not improve, valves are stick-
ing or seating poorly.
c. If two adjacent cylinders indicate low compression
and injecting oil does not increase compression, the
cause may be the head gasket leaking between the
cylinders. Engine coolant and/or oil in cylinders
could result from this defect.
Compression Pressure Limit ChartThis chart may be used when checking cylinder com-
pression pressures. It has been calculated so that the
lowest reading number is 75 percent of the highest
reading number. See Figure 6G-2.
EXAMPLE: After checking the compression pressures
in all cylinders, it was found that the highest pressure
obtained was 182 psi The lowest pressure reading
was 145psi.
By locating 182 in the maximum col-
umn, it is seen that the minimum allowable pressure
r-.__MAXIMUM
PRESSURE
POIJNWW. INCH
--
134
136
138
140
142
146148
150
152
154
156
158160lb2
164166168170172
174
176
178
180182184
186MINIMUM
PRESSURE
POUNDS/
SQ. INCHHAXIMUM
‘RESSURE
‘OUNWiQ. INCHMINIMUM
PRESSURE“OUNWX?. INCH
101188I41I02190142104192144105194145107196147II0198148Ill200150
113202151
114204153
115206154
117208156118210157120212158
121214160123216162
124218163
126220165127222166129224168131226169132228171133230172
135232174136234175138236177140238178
Figire 6G.2 Compression Pressure Limit Chart
is 136psi. Since the lowest reading obtained was 145
psi,
the car is within limits and the compression is
considered satisfactory.
Spark Plugs1. Inspect, clean and regap or replace spark plugs as
required. Correct gap is
,030.2. Install spark plugs. Tighten to 30 lb.ft.
Secondary Ignition System1. Inspect ignition cables for broken, swollen or
deteriorated insulation.
2. Check terminal ends and condition of rubber
boots. Replace as required.
3. Inspect the condition of the distributor cap and
rotor.
4. Clean the ignition coil and inspect for cracks or
carbon paths which could cause high voltage leak-
age.
Distributor Contact Points1. Inspect distributor contact points and replace or
adjust as necessary
(.016 gap).

6G- 68 1973 OPEL SERVICE MANUAL
SPECIFICATIONS
TUNE-UP SPECIFICATIONS AND ADJUSTMENTS
Voltage Regulator
Voltage Regulator Setting in Volts at2500 Engine RPM. . . . . . . . . . . . . . . . . . . . . .14+.5
Ignition Coil
Ignition Coil Current Draw, Amperes at 12.5 Volts
Engine Stopped
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . \
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . \
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . \
. . . . . .3.8
EngineIdling. . . . . . . . . . . . . . . . . .._.....................................................................\
........................... 2.3
Total Advance (Centrifugal and Vacuum), Engine Degrees at 3600 Engine \
RPM......29-38
Centrifugal Advance, Engine Degrees and RPM
Start Advance, atRPM
........................................................................\
................ 1000-1200
Medium Advance, Degrees at RPM..............................................................7.5-15 at 1400
Maximum Advance, Degrees at RPM
..........................................................28-32 at 3600
Vacuum Advance, Engine Degrees and In. of Vacuum Start Advance..
........................................................................\
.................-5at2.9-4.1 In.
Maximum Advance..........................................................................\
........1-5at4.5-5.0In.
Vacuum Retard, Engine Degrees at Closed Throttle............................................................-5
Condenser Capacity in
MicroFarads........................................................................\
.......23-.32
Breaker Spring Tension in Ounces........................................................................\
......14 to 19
Breaker Point Gap in Inches
........................................................................\
......................,016
Dwell AngleinEngine Degrees........................................................................\
.......... 50+3
Firing
Order........................................................................\
............................................l-3-4-2
Spark Plug or Coil Cable,Max.Resistance in Ohms
..................................................
10,000
Spark Plugs
Make and Model Production........................................................................\
............AC42FS
Make andModel
-Replacement........................................................................\
..........AC42FS
If carbon fouling occurs, use
........................................................................\
............AC43FS
Spark Plug Torque in
Lb.Ft.........................................................................\
.........................30
Spark Plug Gap in Inches........................................................................\
..........................,030
Valve Lifter Adjustment
One full turn (clockwise) after zero clearance is obtained - refer to Valve Adjustment
Procedure
Ignition Timing
Align timing marks with distributor retard hose disconnected and plugged\