1973 OPEL GT-R change time

WHEELS AND TIRES3G- 61Cornering Tread WearThe modern independently-sprung automobile al-
lows the driver to negotiate turns at a high rate of
speed with a greater feeling of safety. This fact is
responsible for a comparatively new type of tread
wear that can easily be mistaken for toe or camber
wear.When a car is making a turn, the tires are supposed
to be rolling in a circle. When the turn is made at
high speed, however, centrifugal force acting on the
car causes the tires to be distorted sideways and to
slip or skid on the road surface. This produces a
diagonal cross type of wear, which in severe cases
will result in a fine or sharp edge on each rib of the
tire treads.
Cornering wear can be distinguished from toe or
camber wear by the rounding of the outside shoulder
of the tire and by the roughening of tread surface in
this section denoting severe abrasion. See Figure
3G-7.No alignment or tire pressure cahnge can be made
that will relieve cornering wear. Only the driver can
effect a cure and that is by slowing down on curves.
Heel and Toe Tread WearHeel and toe wear is a saw-tooth effect with one end
of each tread block worn more than the other.
The end which wears is the one that first grips the
road when the brakes are applied. High-speed driv-
ing and excessive “se of the brakes will cause this
type of irregular tire wear. This type of wear will
occur on any type of block tread design. See Figure3G-7.
Heel and toe wear is not so prevalent on the rear tires
because of the propelling action which creates a
counteracting force which wears the opposite end of
the tread block. These two stresses on the rear tires
wear the tread blocks in opposite directions and re-
sult in more even wear while on the front tires, the
braking stress is the only one which is effective. This
may be counteracted by interchanging tires.
A small amount of irregular wear, slightly
saw-toothed in appearance, at the outer segments of tires
is a normal condition and is due to the difference in
circumference between the center and the outer
edges of the tire tread. This saw-toothed appearance,
however, will be exaggerated by underinflation, im-
proper toe-in, or both.Cupped or Scalloped Type Tire Wear
Cupping or scalloping is associated with wear on acar driven mostly at highway speeds without recom-
mended tire rotation. Factors which promote cup-
ping include underinflation, incorrect toe-in setting
or camber setting, and steady highway speeds on
smooth, paved surfaces as opposed to gravel or
rough asphalt.
The following recommendations suggest action that
may be taken to help prevent cupping.
1. Rotate tires as recommended in Figure
3G-6.2. Frequently inspect front tires for irregular wear
due to underinflation, improper toe-in setting, or
camber setting. Regardless of the original cause of
cupped tread wear on either front tire, no alignment
or balance job, however perfect, can prevent future
excessive wear of the spots. Once a front tire acquires
flat or cupped spots, additional wear will continue at
a rapid rate. At the time of correction, however, the
cupped tire should be interchanged with a rear tire
on which the tread runs true. The cupped tire will,
to a certain degree, true itself on a rear wheel.
Although not normally the cause of cupping, the
following factors can contribute to the problem.
Looseness of parts in the suspension system, such as
worn steering knuckle ball joints, loose wheel bear-
ings, inoperative shock absorbers, and any excessive
looseness throughout the steering system all tend to
allow the front wheels to kick around and, if any of
the wheel alignment factors are incorrect, irregular
spotty tire tread wear of one type or another may
result.
Wobble or runout of a tire, either front or rear, due
to bent wheel or to tire being improperly mounted
will cause uneven wear.
MAINTENANCE AND ADJUSTMENTSDEMOUNTING AND MOUNTING
TUBELESS TIRESDue to “se of symmetrical rims, tires must be
mounted over the narrow rim shoulder i.e., over out-
side rim flange.
When demounting a tubeless tire “se care to avoid
damaging the rim-seal ridges on tire beads DO NOT
USE TIRE IRONS TO FORCE BEADS A WA Y
FROM WHEEL RIM FLANGES.
When tire is removed, inspect it carefully to deter-
mine whether loss of air was caused by puncture or
by improper
tit of beads against rim flanges. If im-
proper fit is indicated, check wheel as follows: Do
not reuse dented rims.

POWER BRAKE BOOSTER AND MASTER CYLINDER5A- 5ConditionGrabby Brakes (Apparent
Off-and On Condition)
Possible Cause1. Broken or damaged
hydraulic brake lines.Correction1. Inspect and replace, as
“CXXSSary.2. Insufficient fluid in
master cylinder.
3. Defective master cylinder
seals.4. Cracked master cylinder
casting.2. Fill reservoirs with approved
brake fluid check for leaks.
3. Repair or replace, asnecessary.4. Replace
5. Leaks at front disc brake
calipers or rear wheel
cylinders
in pipes or connections.5. Inspect and repair, as
necessary.Brakes Fail to Release6. Air in hydraulic system.
1. Blocked passage in power
piston.
2. Air valve sticking shut.6. Bleed system.
1. Inspect and repair or replace,
as necessary.
2. Check for proper lubrication of
air valve “0” ring.
3. Broken piston return spring
3. Replace
master cylinder.
4. Tight pedal linkage.5. Repair or replace, as
necessary.
MAINTENANCE AND ADJUSTMENTS
CHECKING BRAKE BOOSTER OPERATIONThe operation of the brake booster can be checked by
simple means and without any special devices.
1. With engine off, first clear the booster of any
vacuum by depressing brake pedal several times.
2. Then depress brake pedal and start engine. If the
vacuum system is working correctly, the brake pedal,
kept under even foot pressure, moves farther down-
wards due to the additional pressure developed by
the booster. Should the brake pedal not move farther
downwards, the vacuum system is deficient. In this
case check the vacuum hose to booster, to vacuum
control valve and to engine intake manifold connec-
tions.3. If the vacuum system operates properly, the defect
is in the brake booster itself. A dirty filter impairs oreven prevents air from entering into the booster and
thereby the formation of a difference in pressure in
the vacuum cylinder.
Repairs cannot be carried out on the brake booster.
If no deficiency can be found in the vacuum system
or filter, the brake booster has to be replaced.
Under normal operating conditions the brake
booster requires no service. However, under adverse
conditions such as frequent driving on sandy or
dusty roads, the filter and sound deadener should be
replaced occasionally. To do so, the brake booster
must be removed but it isn’t necessary to detach the
master cylinder.
BRAKE BOOSTER FILTER SERVICEUnder normal operating conditions the filter need
not be exchanged for a new one.
Under adverse operating conditions
- frequent driv-

58.201973 OPEL SERVICE MANUAL
half, and blow out pistons, carefully regulating air
flow. When removing pistons, proceed with extreme
caution and always keep the fingers ofthe hand hold-
ing the brake caliper away from the piston.
Figure 55.33 Removing Caliper Rim Half Piston
Figure 58-34 Removing Caliper Mounting Half Piston
4. Pry rubber fluid seals out of the annular grooves
in the caliper half bores. See Figure
5B-35.5. Check all parts of the brake caliper for wear. If the
caliper half bores are scored or rusted, use a new
complete brake caliper and friction pads. Small, light
rust spots in the caliper half bores or on the pistons
can be removed with fine emery cloth. If pistons are
damaged, even though the caliper half bores are inFigure 58-35 Removing Rubber Fluid Seal From
Caliper Boresgood condition, the piston must be replaced. The
rubber fluid seals and rubber seals with
clapp rings
for the pistons are to be replaced every time repair
work is carried out on the brake caliper.
6. Thoroughly clean all reusable parts
- complete
brake caliper and pistons
- with denatured alcohol
and dry with compressed air. Prior to cleaning, screw
bleeder valve out of caliper.
7. Lightly coat new rubber fluid seals with brake
fluid and insert fluid seals into grooves of brake
caliper bores.
8. Place brake caliper into vise to install pistons.
After installing one piston, change position of brake
caliper in vise to install second piston. The piston to
friction pad spacer plates should be used as a gauge
to locate relieved edge of piston at 20 degrees to
horizontal during piston installation. See Steps
9-IO-
11-12.9. Place caliper mounting half in vise and coat its
bore and piston lightly with brake fluid. Then push
piston, with hollow end towards brake disc, into the
caliper bore. Turn piston so that the relieved edge
faces downwards at an angle of 20 degrees and facing
in brake disc direction. The guide surface in the
caliper half recess at the brake pipe connection side,
will properly align the piston. Push piston into
caliper bore up to the stop.
10. Change position of brake caliper and install sec-
ond piston in the same manner.
11. Install new rubber seals with clamp rings. Make
sure that the rubber seals are properly seated on the

ENGINE MECHANICAL AND MOUNTS6A- 15New inlet valves must not be refaced or lapped with
grinding compound.The correct angle for the intake
and exhaust valve head is 44 degrees.10. Install cylinder head.
11. Adjust valve clearance. See MAINTENANCE
AND ADJUSTMENTS.
7. Inspect valve guides. Worn or pitted guides can be
reamed to accept valves with oversize stems. Over-
size valves are occasionally used in production.
Oversize valves are marked
’ 1 u “2” or “A” and are
stamped into the valve stem end and also stamped
near spark plug hole. See Figure 6A-22.
Replacing Rocker Arm Studs1. When replacing rocker arm studs become
neces-
sary, remove air cleaner, rocker arm cover and
rocker arm.
8. Reseat valve seats in cylinder head in the following
sequence:
Intake
NOTE:The rocker arm studs are screwed into the
cylinder head. A tapered part of the stem serves to
a void stud loosening.With 45 degrees cutter, remove burnt structure until
a metallic bright seat is obtained. Lightly coat valve
head with red lead, insert it into guide and turn it
under light pressure several times back and forth.
Thereby a contact pattern is obtained and the seat
width can be measured. If valve does not seat per-
fectly all around, lightly recut valve seat to the estab-
lished seat width of
,049” - .059” with 30 degrees
correction cutter.
ExhaustThe directions for reconditioning intake valve seats
apply in principle also to exhaust valve seat recondi-
tioning with the exception that the valve seat width
should be
.063-,073 in. and different cutters are em-
ployed.
NOTE:
: OTse new valve seals whenever
valves are reconditioned.9. Lube valves with engine oil and reinstall valves,
valve springs, caps and cap retainers using J-8062.
Install valve spring with closely wound coils toward
cylinder head. See Figure
6A-24.2. Attach vise grip pliers to stud being removed and
remove from cylinder head.
3. Screw in new stud. Seat tapered part of stud by
striking stud end with a rubber hammer.
4. Place two turned down rocker arm nuts on
threaded part of stud.
5. Torque stud into cylinder head to 29
lb.ft.
Valve Lifter ServiceThe valve lifters can be removed after removing
rocker arm cover and rocker arms.No oversize lifters have been released due to the
insignificant wear of the valve lifters and cylinder
head guides.
Amply oil respective parts and install in reverse se-
quence to removal.
Carry out hydraulic valve lifter adjustment as ou-
tlined in MAINTENANCE AND ADJUST-
MENTS.
VALVE
I SPRING
CLOSE
WOUND
COILS
TOWARD
HEAD6A-24
Figure 6A-24 Valve SpringCONNECTING ROD BEARINGSA connecting rod bearing consists of two halves or
shells which are alike and interchangeable in rod and
cap. When the shells are placed in rod and cap the
ends extend slightly beyond the parting surfaces so
that when rod bolts are tightened the shells will be
clamped tightly in place to insure positive seating
and to prevent turning. Theends of shells must never
be tiled flush with parting surface of rod or cap.
If a precision type connecting rod bearing becomes
noisy or is worn so that clearance on crankpin is
excessive, a new bearing of proper size must be se-
lected and installed since no provision is made for
adjustment. Under no circumstances should the con-necting rod or cap be filed to adjust the bearing
clearance.

6A- 161973 OPEL SERVICE MANUALInspection of Connecting Rod Bearings and
Crankshaft JournalsRemove oil pan.
After removal of oil pan, disconnect two connecting
rods at a time from crankshaft and inspect the bear-
ings and crankpin journals. While,tuming crankshaft
it is necessary to
t&porarily reconnect the rods to
crankshaft to avoid possibility of damaging the jour-
nals through contact with loose rods.
If connecting rod bearings are chipped or scored they
should be replaced. If bearings
are in good physical
condition check for proper clearance on crankpins as
described under, checking clear$nce and selecting
replacement connecting rod beartngs.
If crankpin journals are scored or ridged, the crank-
shaft must be replaced, or reground for undersize
bearings, to insure satisfactory life of connecting rod
bearings. Slight roughness may be polished out withfine grit polishing cloth thoroughly wetted with en-
gine oil. Burrs may be honed off with a fine oil stone.
Use an outside micrometer to check crankpins for
out- of-round. If crankpins are mpre than
,002” out-
of- round, satisfactory life of new ,bearings cannot be
expected.
Checking Clearance and Selecting Replacement
Connecting Rod BearingsService bearings are furnished in standard size and
several undersizes. The clearance of connecting rod
(and crankshaft) bearings may be checked by use of
Plastigage, Type PG-1 (green), or equivalent, which
is soluble in oil.
1. Remove connecting rod cap with bearing shell.
Wipe off oil from bearing and crankpin journal, also
blow oil out of hole in crankshaft.
2. Place a piece of the plastic-type gauge material
Figure 6A-25 Checking Bearing
Cleatance WithPlastic-Type Gaugelengthwise along the bottom center of the lower bear-
ing shell (Figure 6A-25, view A), then install cap
with shell and tighten nuts to 36 lb. ft. Do not turn
crankshaft with gauge type material in bearing.
3. Remove bearing cap with bearing shell, the flat-
tened piece of gauge will be found adhering to either
the bearing shell or the crankpin. Do not remove it.
4. Using the scale printed on the envelope, measure
the flattened piece of gauge at its widest point. The
number within the graduation which closely corre-
sponds to the width of the gauge, indicates the bear-
ing clearance in thousandths of an inch. See Figure6A-25, View B.
5. The desired clearance with a new bearing is.0006”- .0025”. If bearing has been in service it is
advisable to install a new bearing if the clearance
exceeds .003”, however if bearing is in good condi-
tion and is not being checked because of bearing
noise, it is not necessary to replace the bearing.
6. After the proper size bearing has been selected,
clean off the gauge, oil thoroughly, reinstall cap with
bearing shell and tighten nuts to 36 lb. ft.
CRANKSHAFT BEARINGS AND SEALS
Replacement of Crankshaft BearingsA crankshaft bearing consists of two halves or shells
which are identical and are interchangeable in cap
and crankcase. All crankshaft bearings except the
rear main bearing are identical. The crankshaft end
thrust is taken up the rear (No. 5) main bearing.
Figure 6A-26 Engine Crankshaft Bearings
When the shells are placed in crankcase and bearing
cap, the ends extend slightly beyond the parting
sur-faces so that when cap bolts are tightened the shells
will be clamped tightly in place to insure positive

CARBURETOR AND THROTTLE LINKAGE6E- 4512345678Sectional View Of 19 US Carburetor (both barrels)
1 PIug(transition channels, secondary barrel)
6 Float chamber
2Carburetor
cover7Idleairpassage
3Vent tube
8Idleairiet4Transit’
,n iet9 Idle air adjusting screw
5 Transition air iet10 Mixture adjusting screw
6E-1Figure 6E-1 Sectional View of Primary and Secondary Barrels
valve gradually opens and the mixture
become+leaner. During this process, the abutment lever
changes position on the fast idle cam, further closingBefore starting a cold engine slowly, depress the ac-celerator pedal three times before engaging the
starter.
the throttle valve until, the engine is at normal oper-
ating temperature, the choke valve is wide open and
the throttle valve is in slow idle position.
Idle and Part Throttle SystemA choke diaphragm is connected to the intermediate
lever of the choke valve spindle through a pull rod.
The vacuum, which develops below the throttle
valve, takes effect on the diaphragm through a
vacuum passage. See Figure
6E-4. As soon as the
engine starts, this vacuum pulls the choke valve
slightly open; the amount of choke valve opening
depends on the amount of vacuum, which depends
on the engine load. Therefore, with a light engine
load, the choke valve will open slightly; with a heavy
engine load, the valve will close slightly to give a
richer mixture as required for this engine load.At engine idle grid during low speed (part throttle)
operation, fuel is drawn from the emulsion tube bore,
controlled by the idle jet and mixed with air entering
through idle air bleeds (Figure 6E-1) and ports in thethrottle body. This mixture is drawn downward to
the three ports near the throttle valve. When the
throttle valve is closed, the mixture is drawn from
the lowest port and mixed with air by-passing the
throttle valve to form the idle mixture.
Turning the idle mixture screw (Figure
6E-1) inward
results in a leaner mixture, and turning it out results

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.

98-20 1973 OPEL SERVICE MANUAL
If we were to put a thermometer in the cold drain
water, we would see the temperature gradually creep
upwards. That is to be expected because heat is flow-
ing into the cold water making it warmer. Before
long the water would be as warm as the stored foods.
Then the water could no longer attract heat because
heat will not flow from one warm object to another
equally warm object. Since we no longer can draw
heat out of the foods we no longer are cooling them.
Now, let’s see what happens when we put ice instead
of cold water into the ice-box. This time, we’ll set the
thermometer on top of the ice (Fig. 9B-5). When wefirst look at the thermometer, it reads 32 degrees. A
couple of hours later, we open the ice compartment
door. The ice block is smaller because some of the ice
has already melted away
- but the thermometer still
reads 32 degrees. Again, still later, even more of the
ice has melted, yet the termometer continues to read
32 degrees. So long as any ice remains, no matter
how much of it has melted away, the temperature of
the ice stays right at 32 degrees.
All this time the ice has been soaking up heat, yet it
never gets any warmer no matter how much heat it
draws from the stored food. On the other hand, the
cold drain water got progressively warmer as it
soaked up heat. Why is it the addition of heat will
make water warmer yet won’t raise the temperature
of ice above the 32 degrees mark? If we till one
drinking glass with ice and another with cold water,
and put both glasses in the same room where they
could absorb equal amounts of heat from the room
air, we will find it takes much, much longer for the
ice to melt and reach room temperature than it did
for the water in the other glass to reach the same
temperature. Obviously, most of the heat was being
used to melt the ice. But it was the heat that appar-
ently disappeared or went into hiding because if
couldn’t be located with a thermometer. To best de-
scribe this disappearing heat, scientists turned to
Latin for the right word. They chose the word “la-
tent” which means hidden.
Latent Heat
So latent heat is nothing more nor less than hidden
heat which can’t be found with a thermometer.
What happens to the latent heat? Where does it
disappear to? At first it was thought it was in the
water that melted from the ice. But that wasn’t ex-
actly the right answer because, upon checking water
temperature as it melts from ice, it will be found that
it is only a shade warmer than the ice itself. It is not
nearly warm enough to account for all the heat the
ice had absorbed. The only possible answer is that
the latent heat had been used up to change the ice
from a solid into a liquid.
Many substances can be either a solid, or a liquid, ora gas. It just depends on the temperature whether
water for example was a liquid, or a solid (ice), or gas
(steam) (Fig.
9B-6).Figure 99-6 Temperature Determines State of Water
If we put some water in a tea-kettle, set it over a tire
and watch the thermometer as the water gets hotter
and hotter, the mercury will keep rising until the
water starts to boil. Then the mercury seems to stick
at the 212 degrees mark. If we put more wood on the
fire, despite all the increased heat, the mercury will
not budge above the 212 degree mark (Fig.
9B-7).Figure 98.7 Boiling Water Never Exceeds 2 12
DegreesEven though many housewives won’t believe it, no
matter how large or hot you make the flame, you
can’t make water hotter than 2 12 degrees. As a liquid
changes into a gas, it absorbs abnormally great
amounts of heat without getting any hotter. Here is
another instance where heat disappears.
Now we have two different kinds of latent heat,
which are quite alike. To keep their identities sepa-
rate, the first one is called latent heat of fusion. Since
fusion means the same as melting, it is a good de-
scriptive name. The other kind is called latent heat
of vaporization because‘ that means the same as
evaporation.
It may seem as though we have drifted into a story