Opel GT "Things to Know" (Top Ten List)
This is a list of 10 things all Opel GT owners (or, persons buying an Opel GT) need to know.
(This is primarily for “new” or prospective GT owners, but also includes “refresher” tips for all.)
All vehicles have their idiosyncrasies -- the Opel GT is no exception -- but with specific
attention and repairs, including reference to, and use of, OMC tech tips, more time can be
spent driving and enjoying your vehicle.
1) Identify What Year Is It
Knowing the model year of an Opel GT, with its VIN number
(located on the firewall plate — as seen on right — GT model
numbers start with either "94", "77" "0Y0"or "93") or by certain
parts types, will help you to know what major year-to-year parts
or service procedure changes apply to your vehicle.
(To learn more, see the "What Year Is It" page at www.opelclub.com, or view the original article in the Nov. 1995 OMC Blitz).
2) Inspect Body and Drivetrain Condition
The Opel GT is now a 30+ year old all-steel unibody vehicle, so when inspecting a GT for purchase
you need to check for rust. Try to purchase cars you can see in advance (when not on Ebay),
and pay closer attention to vehicles “doctored” for sale by dealers.
The areas of common treatable rust are below the battery mount area in the
front belly pan and behind the rear wheels. Difficult rust repairs (shown at right)
are located in the floor pan near the rocker panels, below the windshield, and
on the doors above the mid-line of the exterior panels. Be wary of GT's from
the Northern US, as suspension bolts also rust solid and the upper
Extensive GT Rust Area
shock tower (top of front shocks) rusts through, in critical stress areas.
Also avoid body damage -- Use a magnet to locate “bondo” body-filler areas.
When damage is in the rotation area of the GT headlights, it can be very difficult to repair to an aesthetic satisfaction.
Door and side panel repair is easier, with used sheet metal replacements (when available).
Generally, when a choice is available, we suggest buying a higher-priced undamaged GT over lower-priced
GTs requiring repairs to rust or damaged areas.
Verify the engine will turn over, by removing the spark plugs,
squirting a teaspoon of oil into each cylinder, then use a
19mm wrench to rotate the front crankshaft bolt in a
clockwise direction. Be patient — In some cases it takes a
few days for engine to move freely.
Also verify vehicle can be moved, by pushing it to loosen
grip of the brake and transmission/clutch and rear axle parts.
Inspect critical rubber suspension and torque tube parts.
If battery is available, check wiring and briefly test
operation of the dash controls and light circuits.
It’s a good idea, whenever possible, to tow a newly-purchased
vehicle home on a 4-wheel dolly or flatbed for added safety.
Decide on Mechanics or Do-It-Yourself
Many mechanical repairs on the Opel GT can be done by the
owner, presuming a reasonable skill level, correct parts, some
metric or special tools, instructions, and some time for the job.
The advantages of this approach include saving the costs
of mechanic's labor, and learning about your GT as you go along.
GT owners have found doing this can be personally empowering!
Others have hired professionals to work on their car.
The advantages are that they can bring certain expertise to
the job (particularly recommended for machine work on
engines and transmissions, and skilled paint & body work).
To avoid getting burned on GT service by mechanics:
-Research the reputation of the shop (ask prior customers),
and shop around. (One place is at www.opelgt.com).
-Meet and question the mechanic doing the actual service
work (not just a salesman or shop owner) and judge by his
attitude, credentials, work area and tools (ie ask to see his
torque wrench, vehicle lift and engine lift),
-Insist the mechanic read written “tech tip” procedures prior
to starting a job (particularly when unfamiliar with Opels),
-Get written time & cost estimates in advance of starting work,
-Expect more repair work in the middle of a job (rusty bolts),
-Rely on machine experts to do rebuilds (engine, trans, axle).
-Report unresolved complaints to government agencies or BBB.
Also learn the difference between the value of a "rebuilt" GT
(with parts replaced as needed) and a "restored" GT (all parts
reconditioned or replaced with new parts), before authorizing
a repair job of several thousand dollars (that in some cases
may exceed your wishes or the resale value of the vehicle).
Acquire Service Manuals
No single Opel Service Manual contains all the information you
need to repair your GT, and not even the factory manual is 100%
correct (which is why OMC “tech tips” were written).
The best combination (in general) is the 1971-1973 factory Opel
shop manual combined with the aftermarket "GT Owners
Workshop Manual" and a reprint of the Electrical Schematic
(the best schematic is sold by DESTEC on Ebay for about $25),
but this can vary with the actual model year of parts in your GT.
To learn more, see the “GT Service Manual" page at
www.opelclub.com, or the original article in the April 1995 Blitz).
5) Inspect & Repair Critical Components
Your first priority should be safety, which begins with awareness.
The Opel GT headlight wiring (at the moving mechanisms) must
be replaced if it is the original 30+ year-old set. The factory
Rubber insulation breaks off, which causes short circuits
(damaging pricey headlight relays) and in some cases catches fire.
The area to inspect, under the headlight lids, is shown at right.
GT Headlight Rewiring instructions are online in the “tech tip” index, at the
www.opelclub.com website, or view the original article in the August 2004 OMC
The Opel GT ignition switch is prone to internal carbon buildup
and sudden failure, which immobilizes the car.
This scenario can be put off, by carefully disassembling the
steering column and cleaning the interior switch with WD-40,
and/or installation of a protective Radio Shack #275-226
4-prong relay (shown at left) in the starter circuit.
Diagnosis & Installation instructions are online at www.opelclub.com
(in “tech tip” index for electrical system) and in the Jan 2006 OMC Blitz.
Also inspect the vent hoses attached to the gas tank (behind the spare tire area) which are prone to
disintegration, causing release of hazardous gas vapor in the vehicle interior. Lift the GT, so other
component systems like exhaust & suspension, can be fully checked before operation. Test the brake pedal
very gently to give the seals in the master cylinder some light motion: If the rubber brake hoses appear stiff and
wheel cylinders leak, it's a good idea to just replace them.
6) Restarting Procedures
Generally it's a good idea to just go ahead and replace all the fluids and filters
in a newly-acquired GT: This includes the engine oil, transmission oil, rear axle oil,
and brake fluid. Flush the cooling system to remove internal scale, and particular
attention should be given to cleaning out the gas tank, fuel hoses and carburetor.
Replace the radiator hoses, fan belt, and battery.
Once the engine turns easily, check starter operation, then perform a compression test
to verify a minimum measurement of 125 psi in each cylinder. (This may also require
a valve adjustment on individual cylinders, to maximize compression output).
Opel 1.9 Compression Test instructions are online at www.opelclub.com and in the June 2006 Blitz.
Identify Parts Differences and Availability:
Try to shop in advance of your needs, as high demand
sometimes causes delays in availability for certain GT parts.
Make list of parts you want to purchase, then check the parts t
types match those actually on your car.
Example GT Rear Brake Shoe Styles:
Examples of parts to inspect and write down for reference:
Early Style (ball & folded lever) at Top.
Cylinder head: Does it have solid or hydraulic type lifters?
Late Style (hook and stirrup) at Bottom.
Is it a early 10 or late 12 bolt style? Does it have 3 or 4 camshaft bearings?
Rear Axle: Does it have an early or late model shafts and wheel bearings?
Parking Brake Cable and Rear Shoes:
Are early or late model parts installed? (Shown at right)
Condensor: Does it have a square or round-hole type insulator?
Additional Information is available online at www.opelclub.com, or in
article titled "What Year Is It" in November 1995 OMC Blitz.
Daily Operation Tips:
The original Solex 32DIDTA carburetor can be nearly impossible to tune
properly. Most Opel GT's have a Weber 32/36 DGEV carb (at right) installed,
for reliable performance and better mileage. Install with a thick-style
carb base gasket, sealed on all both surfaces with Permatex High-Tack
to prevent vacuum leaks. (Weber carb tips are in the Dec 1995 & July 2000 OMC Blitz).
Keeping a GT in tune means maintaining correct .018" point gap (50 degrees
dwell on meter, at left) at zero TDC of the distributor. Check distributor operation
when a tune doesn't last, or consider an upgrade to an electronic ignition to ensure
accurate ignition timing. Any vacuum leaks at, or to, gaskets or hoses connected to
the intake manifold also affects timing, so test and seal all junctions for leaks.
(The GT Tune Up Procedure is online at www.opelclub.com, and in the June 2006 Blitz)
Transmission fluid leaks quickly cause transmission failure on GT's.
Always wipe then refill the transmission, then park over a cardboard
or paper surface to check for drip sources. Replace seals & gaskets
immediately when leaks occur, to avoid costly repair & replacement.
(Clutch and Transmission Tech Tips are in the March 1995 Blitz).
Opel parts to carry: Keep a Fan Belt, Water Pump, Fuel Pump, Ignition
Points & Condensor, Lower Radiator Hose, Hose Clamps, & Gaskets in GT.
Tools to carry: Metric 8, 10, 11, 13, 15, 17 & 19mm wrenches, "special"
8, 10 & 12mm serrated bits, feeler gauges, 13mm stubby & 11, 13
& 15mm obstruction wrenches. (Keep parts & tools in rim of the spare).
Supplies to carry: Tire & gasket sealers, starter spray and flashlight.
Another safety tip is installing a 3rd brake light for visibility at the rear.
Summer GT Operation: Clean the radiator, install a
160-degree thermostat, check the water pump & coolant
hoses, & insulate fuel lines to prevent vapor lock.
Additional Summer Tips are in the May 1995 OMC Blitz newsletter.
Winter GT Operation: Clean the heater valve, install a
180-degree thermostat, upgrade the alternator,
lube headlight cable and locks with WD-40, inspect
rubber weather-stripping, floor plugs and shift boot,
and consider use of Rain-X on windows for visibility.
Additional Winter Tips are in the Jan 1995 OMC Blitz newsletter.
10) Consider Upgrades & Encourage Non-Members to Join OMC!
Once your GT is reliably running, (if you haven’t already — we suggest to join the OMC, and)
read Blitz newsletters for additional ideas for more performance and restoration of your GT.
GT upgrade projects are best done component group-by-component group, which is how the
OMC tech tip index (available online at www.opelclub.com & in the May 2004 OMC Blitz)
is laid out: Body, brakes, clutch, engine, interior, suspension, etc. Start with projects for safety,
then performance, & finish with cosmetics. Always do tech research & purchase parts in advance.
Then build your own ready-reference OMC newsletter collection. When you have OMC's
peer-reviewed tech tips in hand, the job is much easier going -- because it's already been done!
(credit: “Mr. Badwrench” Opel Mechanic Cartoon: Tina S./NAOGTC Issue #55)