The GT6 began when in 1963 Triumph were considering extending their range of cars. Following a discussion between Michellotti and Triumphs technical director regarding designing a fastback body for the popular Spitfire, a spitfire was delivered to Michellotti in Turin.
Later that year the car was finished and returned to triumph, christened the Spitfire GT. His design added too much weight to the car so the idea was shelved but not forgotten and in 1964 the Spitfire GT project became official policy . The decision to turn it into a six-cylinder car was the result of progress with the up-grading of the Vitesse to a 1998cc. It was a bit of a squeeze getting the 1998cc six-cylinder engine into the Spitfire’s engine bay, but by creating a rather complicated cooling system and a large bonnet bulge they managed it. Assembly of the production cars commenced in July 1966 and by 1967 the build rate had steadied at 500-600 cars per month.
In Autumn 1968 the GT6 Mk2 was introduced (known as the GT6+ in the US), it had revised body styling incorporating a raised front bumper and the rear over riders had now been removed The car was also fitted with an advanced rear suspension layout.
This used a reversed lower-wishbone with double-jointed drive shafts, reducing camber change from 21 deg to 7 deg 20 mins. The effect on the handling of the GT6 was very impressive. The Mk2 also acquired a new cylinder head, borrowed from the TR5, together with a revised camshaft profile this resulting in an increase of bhp from 95 @ 5000rpm to 104 @ 5300rpm. In 1970 the Mk2 was given a face lift this included new reclining seats, matt black facia surround, new steering wheel and badges.
In November 1970 the GT6 Mk3 was launched . In line with the Spitfire MkIV, the tail was “chopped-off” and the bonnet flattened out. The rear roof line of the GT6 was altered and the petrol cap and door handles ceased to protrude. The US market being the largest customer was all important to Triumph and in 1972 to meet US emission regulations the US specification cars saw a change in carburettor, piston, ignition, distributor and camshaft design reducing the cars power to 95bhp.
In 1973 the GT6 was face lifted, new fabric upholstery, new style intruments and for the European market servo assisted brakes and “sundym” glass. The US specification cars emission control was also further controlled bringing the power output down to just 79bhp, little more that the UK spitfire. All this extra cost on the car meant the car was now not so competitive so the advance rear suspension was converted back to the old swing axle type to keep the car comparable with its nearest rival the MGBGT. Optimism was high in the sales department but in reality the bell was tolling. The safety legislation enforced by the US market meant a considerable increase in weight – the exhaust emission regulations badly affected the power of the six-cylinder engine and sales dropped…and dropped.
No official death certificate was released but on the thirtieth of November 1973 the last two GT6s produced quietly left the factory.
The engine has the fairly solid block, but has problems with low oil flow to the valve gear. Listen for excess rattle around the valve gear when the engine is warm; it might mean some work is needed. If possible check the compression, it should be in the 175-185 range (cold).
This is the car’s main problem area. Listen for excess noise and feel for worn synchros. If you suspect problems here you can nearly guarantee that a new\recon box will be required.
The selector linkage also suffers from worn bushes which can make gear selection awkward. Suspension / driveshafts:
If the car is a Rotoflex car check the state of the rotoflex couplings (look for cracks in the rubber donuts), if these let go they tend to destroy the stub driveshafts – can be expensive!
Listen for excessive differential noise.
Listen for universal joint clunks. Expect that at least one U joint will be loose and want replacement. These are all fairly cheap and available, but a pain to install. Same for all the rubber bits in the suspension. Worn rear radius arm bushings, especially, will cause slightly weird handling over bumps.
Check the steering rack gaiters for tears and the rack mounting bushings for play. Overdrive:
If it works, great. If it doesn’t, you’re probably looking at a replacement.
Body work is more expensive than mechanical work. So you want as rust free a car as possible. If the car has already been restored check for filler and painted over rust with a magnet. Probably the most important thing is the bulkhead; the car relies on this for structural strength. Look to see if the transmission cover mates well; if it doesn’t, you’ll get heat and fumes into the passenger compartment.
Check the battery box area and the floor underneath it – your usual owner will replace the battery box only after it has caused severe rust on the floor under it.
Check the rear shock mountings to the body on Mk2’s and Early Mk3’s. Check for chrome trim: there should be trim strips along the front and rear wings on Mk1’s and 2’s and rear wing only on Mk3’s. Check for bonnet shake and the integrity of the rubber seals at the rear of the bonnet and the inner wheel Arches.
The chassis is a main spine with outriggers. Check the outriggers for rust; they provide most of the transverse strength of the car. Check the rear frame members for rust.
Unless the optional Servo is fitted; before writing off the brakes as weak, make sure the rears have been adjusted.
Look for leaks around the master cylinders.
There are many types of proofing or water inhibiting products on the market, and most of them take the form of a waxy substance which can be sprayed into the body sections and cavities to prevent moisture forming rust. The rust proofer is usually applied either by high pressure gun, connected to a Compressor, or by a hand pump, which is usually supplied in the kit.
The best method is to use a compressor, the hand pump used with care will give you the results you want. The advantage of the compressor system is that the ‘Shutz gun’ comes with the extension probe to get directly into the cavities and the rust-proofing agent atomises into a fine mist which travels well into the corners. The hand pump methods tends to leave a thicker coating.
If you have got a MkIII, this is the place to start, the screen pillars and front roof section are all box sections, and the temperature changes inside the car create condensation inside them which in turn starts to rot the metal from the inside out. You can access the pillars and the front roof from inside the car. At the bottom of the screen pillars, under each side of the dashboard, you will find a hole that leads into the pillar and right up and around to the roof. Push the extension probe of the gun or hand pump up into the pillar as far as it will reach and simply fill the cavity with rust proofer. On Mkl and II cars the screen assembly unbolts but there is no access inside the pillars, the only way it to remove the screen surround and drill two small holes at the base of each pillar.
The main area that rots here is the bottom edge or lip and the outside corners of the skin area (the area you see when the tailgate is closed). The best way to obtain access here is to remove the lock mechanism from the tailgate itself, which will give you about a one inch hole — the extension probe should go right round the corner inside here.
Next remove the boot floor, spare wheel and trim panels above the lights, either brush or spray rust proofer onto the underside of the area that forms the boot shut panel (adjacent to the boot catch) as again condensation forms under here all the time.
You can gain access to the rear wings at the back through the boot area — push the probe along the wing as far around the wheel arch as possible. Give an enthusiastic coating to the cavity at the rear next to the boot floor (where the bumper brackets are) as this generally is a problem area. To access the front part of the back wing and the end of the sill, you may need to remove the rear quarter trim panels — once they are out you will find a nice large hole to spray with rust proofer.
Outer: If it’s a genuine outer it will have three small holes along the bottom outer edge, perfect for the extension probe. Then through the hole in the back inner wing (under the quarter trim panel) you can access the outer sill also, so spray a load in there. At the front, the best thing to do is drill a small hole in the sill end panel (the flat plate on the end of the sill behind the front wheel), make sure there is plenty of proofer around the hole and seal it after with a small hung. Alternatively, the carpet can be carefully removed from inside the front footwell, against the bulkhead side, a small hole drilled here and the carpet replaced.
Inner: If you remove your seats and then very carefully remove the strip of carpet stuck to the inner sill, you will find two elongated holes where you can get plenty of material in, and then stick the carpet back again.
Areas to treat here are the nose / reinforcer section on MkllI cars, and the sidelight areas on Mkl and II cars. On all models, remove the headlights and spray plenty of proofer into the area. On Mklll cars use a paint brush to force as much as possible into the nose section (where the headlight wires run). Finally, try to run the rust proofer around the wheel arch sections between the inner wheel arch assembly and the main wing —the more the better here as it cannot be seen and can save you whole new wings later on.
Remove the sidelight assembly and spray in through the aperture.
Below is a list of the commision numbers used throughout the life of the GT6.
| Model | Comm No. | Engine | Gearbox | Diff. | Ratio |
|---|---|---|---|---|---|
|
Mk1 |
KC |
KC |
KC |
KC |
3.27 |
|
Mk2 |
KC50001 on |
KC50001 on |
KC |
KC |
3.27 |
|
|
|
|
|
KD |
3.89 |
|
GT6+ USA |
KC50001 on |
KC50001 on |
KC |
KC |
3.27 |
|
|
|
|
|
KD |
3.89 |
|
Mk3 |
KE |
KE |
KE |
KC |
3.27 |
|
|
|
|
|
KD |
3.89 |
|
Mk3 USA |
KF |
KF |
KF |
KC |
3.27 |
|
|
|
|
|
KD |
3.89 |
