TRIUMPH GT-6
 

 

1.0 Background & specifications

The Triumph GT-6 was produced from 1966 to 1973. Conceived from the idea of a 'fastback' version of the popular Spitfire, it used many parts currently in production at Triumph to assemble onto a modified Spitfire chassis the running gear & suspension of Triumph's two-litre 6 cylinder Vitesse sedan. The bodywork was designed by Michelotti.

The car was intended for sale not only in the UK, but export markets. Variations for the cars manufactured for these different markets were for the most part accommodations for right-hand drive or left-hand drive; and particular UK, USA, German, & Sweden requirements.

Three basic versions of the GT-6 were produced over time: the original GT-6, the GT-6 Mk2 (sold slightly modified as the GT-6+ in USA, & the GT-6 Mk3.

1.1   GT-6 models


1.1.1   GT-6

1.1.1.1   Production overview

1.1.1.2   1967 model

1.1.1.2.1   Features & options

1967 GT-6 Features & options (USA market)
Features
Wire wheels standard
Chrome-spoked steering wheel
Chrome-bezel gauges
Factory options
Laycock de Normanville overdrive
AM or AM/FM radio
Front & rear bumper guards
Catalog options
Seat belts

1.1.1.2.2   Contemporary Reviews

Road & Track, April 1967 (USA)
Price as tested $3309
Top speed 107 mph
Acceleration,
0-1/4 mi
18.8 sec
Fuel consumption, normal driving 22-26 mpg
Fuel consumption, cruising range 250-300 mi
Weight distribution (with driver), front/rear, % 56/44
Frontal area 14.9 sq ft
Usable trunk space 6.6 sq ft
Quotes "Lively, quiet and nimble, with an outstandingly smooth engine."
"Besides refinement, torque is its stock in trade. It's one of those engines that doesn't seem to care what gear is engaged behind it."
"We approach any car with conventional swing axles with a little apprehension but we found that the GT6 could not be faulted on its handling."
"Breakaway is smooth and one gets the feeling that the car has a degree of oversteer that can be enjoyed and utilized by a moderately skilled driver while never crossing up an unskilled one."
"The layout of the instruments isn't as good as it might be."
"The GT6 isn't a tall man's car. Our tallest driver, who is 6 ft 3, found himself too cramped to drive it with any degree of pleasure and our two 6-footers complained of their heads touching the roof."
"It has no parallel and it's worth the money."



1.1.2   GT-6 Mk2 / GT-6+

1.1.2.1   Production overview
The GT-6 Mk2/GT-6+ had major revisions from the original GT-6 in bodywork & suspension. Bodywork revision included addition of vents in the bonnet.

The rear suspension redesign replaced the swing-axle rear suspension with a semi-independent arrangement incorporating a rotoflex coupling on each side, & the result was improved handling.

Inside changes included a change to black-bezel gauges from the previous model's chrome-bezel gauges, & a 3-point safety harness.

The GT-6 Mk2 was not sold in the USA. The USA got the GT-6+ instead, a variation of the GT-6 Mk2. The GT-6+ differed only in engine specifications & the addition of evaporative loss equipment to accommodate the new federal emissions requirements.

1.1.2.1.2   Differences between GT-6 Mk2 & GT-6+

1.1.2.3   1968 model

Features & options (USA market)
Features
Dual circuit hydraulic brakes
Steel wheels w/mag-type wheel covers standard
3-point safety harness
Perforated Ambla-covered, contoured bucket seats w/integral head restraints
7 baked enamel body colors available
Four interior trim colors available
Factory options
Laycock de Normanville overdrive
AM or AM/FM radio
Front & rear bumper guards
Wire wheels
Magnesium wheels
Roof rack
A complete line of Sports Car Club of America approved competition equipment for racing available from Triumph Competition Department


1.1.2.4   1969 model
Features & options (USA market)
Features
Dual circuit hydraulic brakes
Steel wheels w/mag-type wheel covers standard
3-point safety harness
Leather-covered steering wheel & matching leather-covered gearshift lever
Perforated Ambla-covered, contoured bucket seats w/integral head restraints
Tinted rear window
Electric rear window demister
Dipping rear-view mirror
Factory options
Laycock de Normanville overdrive
AM or AM/FM pushbutton radio
Front & rear bumper guards
60-spoke wire wheels
Aluminum wheels
Magnesium wheels
Roof rack
Ski rack attachment
Rubber mats
Cigarette lighter
A complete line of Sports Car Club of America approved competition equipment for racing available from Triumph Competition Department


1.1.2.5   1970 model
Features & options (USA market)
Features
Wheels
Steel wheels w/mag-type wheel covers standard
Brakes
Dual circuit hydraulic brakes
Body
White coach stripe (pencil stripe)
Black-painted windshield frame
Tinted rear window
Electric rear window demister
Front & rear side marker lights
Laminated windshield with high-impact interlayer
Swing-out rear quarter lights
Cockpit
Quick-release seat belts
Door operated courtesy light
Combined ignition lock, accessory control & starter control; anti-theft steering column lock incorporated with ignition lock
Ignition key audible warning device
Three-spring-spoked steering wheel with black padding
Gear shift lever w/leather cover matching steering wheel
Individually reclining & adjustable Ambla-covered, contoured bucket seats w/integral head restraints & horizontal pleats
Safety breakaway rear-view mirror
Under-dash parcel shelves
Factory options
Laycock de Normanville overdrive
AM or AM/FM pushbutton radio
Front & rear bumper guards
Aluminum wheels
Magnesium wheels
Luggage rack
Ski rack attachment
Rubber floor mats
Cigarette lighter
A complete line of Sports Car Club of America approved competition equipment for racing available from Triumph Competition Department



1.1.3   GT-6 Mk3

1.1.3.1   Production overview
The GT-6 Mk3 had significant body changes, resulting in a car that was plainly a GT-6 but a bit more streamlined. The radiator opening was moved completely below the new front bumper, the new hood had no stamped vents, & door handles were redesigned to recess into the bodywork. The new car was an inch longer & about 30 pounds heavier than the MK2/+.

Inside, the dashboard was redesigned, & the Mk3 was fitted with a revised fuel tank having a capacity 1.25 gallons less than the previous car.

A new engine block was introduced during the Mk3's production run at engine number KE/KF/KG 10,001. The design incorporated recessed rings on the deck of the block around the tops of the cylinders, to locate a revised head gasket.

The engine cooling system became a "no-loss" design with a revised radiator neck & radiator cap rated at 13 lbs. pressure.

During the GT-6 Mk3's production, British Leyland was instituting changes in the manufacture of its cars to reduce parts variations & standardize similar engines across its cars.

1.1.3.2   1971 model

1971 GT-6 Mk3 Features & options (USA market)
Features
Color choices
Damson
Laurel Green
Imperial Blue
Saffron
Sienna
Signal Red
Valencia Blue
White
Options
Laycock de Normanville overdrive
AM or AM/FM radio
Roof rack
Cigarette lighter
Rubber floor mats
Front & rear bumper guards
Bolt-on wire wheels
Racing Equipment: Aluminum or magnesium racing wheels



1.1.3.3   1972 model

1972 GT-6 Mk3 Features & Options (USA market)
Features
Color choices
Damson w/ black or tan interior
Emerald w/black interior
Pimento w/black interior
Saffron w/black interior
Sapphire w/black or blue interior
Sienna w/tan interior
White w/black or tan interior
Options
Laycock de Normanville overdrive
Heavy-gauge anodized aluminum deep-dish wheel trim rings
Chrome rooftop luggage rack, ski-carrier adaptors
Chrome tubular front & rear guards
Cigarette lighter
Custom-made rubber floor mats in black, white, or red
Walnut gear shift knob
AM or AM/FM radio
Koni adjustable shock absorbers
Striping kit



1.1.3.4   1973 model

1973 GT-6 Mk3 Features & Options (USA market)
Features
Color choices
Emerald w/black interior
Mallard w/black or tan interior
Sapphire w/black or blue interior
French Blue w/black interior
White w/black, blue or chestnut interior
Mimosa w/black or chestnut interior
Pimento w/black or chestnut interior
Carmine w/black or tan interior
Sienna w/black or tan interior
Magenta w/black interior
Options
Laycock de Normanville overdrive
Heavy-gauge anodized aluminum deep-dish wheel trim rings
Chrome rooftop luggage rack, ski-carrier adaptors
Cigarette lighter
Custom-made rubber floor mats in black, white, or red
AM or AM/FM radio
Walnut gear shift knob
Wire wheels
Koni adjustable shock absorbers
Striping kit



1.2   Engine

1.2.1   Development history
The GT-6 engine derived from the 1.6 litre inline 6 engine which was originally in the Triumph Vitesse at the start of its production in 1962.

Triumph increased this engine's displacement to 2 litres, & the new engine was first offered when it debuted in Triumph's Vitesse 2-Litre & GT-6 cars in 1966.

The engine's development outside of the GT-6 & Vitesse cars continued by increasing displacement again, by lengthening the stroke, to 2.5 litres. This derived 2.5 litre engine was used in Triumph's later cars such as updating the 2000 series saloons (starting with the Triumph 2.5 PI in 1968) & the TR series (starting with the TR5/TR250 in 1968).

At engine number KE/KF/KG 10,001 in the GT-6, the block was redesigned with recessed rings on the deck around the tops of the cylinder bores, to locate a revised head gasket. The components of the 6 cylinder engine during the GT-6 run were also subsequently changed to allow greater interchange & manufacturing commonality across the 6 cylinder engines in all of British Leyland's car lines.
1.2.2   Engine data & comparison

Engine data & comparison
  GT-6
(early)
GT-6
(late)
GT-6 Mk2 GT-6+ GT-6 Mk3
(early)
GT-6 Mk3
(late)
Notes Non-recessed cylinder bores, has separate pushrod tubes Non-recessed cylinder bores, pushrod tubes cast into block Non-recessed cylinder bores, pushrod tubes cast into block Non-recessed cylinder bores, pushrod tubes cast into block Non-recessed cylinder bores, pushrod tubes cast into block Recessed cylinder bores, pushrod tubes cast into block
Engine block # range KC1 to KC/KD5,000 KC5,001 to KC/KD50,000 KC/KD50,001 to ?   KE1/KF/KG 1 to KE/KF/KG 10,000 KE/KF10,001 to ?
Cylinder head # range            
Camshaft part # 306785 306785,
307621 (USA from engine # KD6915E)
308778 307621 308778 (all markets except USA & Sweden),
307621 (USA & Sweden only)
311399 (all markets)
Number of cylinders 6 6 6 6 6 6
Cubic capacity 122 cu. in.
(1.998 litres)
122 cu. in.
(1.998 litres)
122 cu. in.
(1.998 litres)
122 cu. in.
(1.998 litres)
122 cu. in.
(1.998 litres)
122 cu. in.
(1.998 litres)
Cylinder bore 2.94 in. (74.7mm) 2.94 in. (74.7mm) 2.94 in. (74.7mm) 2.94 in. (74.7mm) 2.94 in. (74.7mm) 2.94 in. (74.7mm)
Crankshaft stroke 2.992 in. (76mm) 2.992 in. (76mm) 2.992 in. (76mm) 2.992 in. (76mm) 2.992 in. (76mm) 2.992 in. (76mm)
Piston shape flat top flat top flat top flat top flat top domed top
Piston area 40.7 sq. in.
(263 sq. cm.)
40.7 sq. in.
(263 sq. cm.)
40.7 sq. in.
(263 sq. cm.)
40.7 sq. in.
(263 sq. cm.)
40.7 sq. in.
(263 sq. cm.)
 
Compression ratio 9.5:1 9.5:1 9.25:1 8.5:1 9.25:1 (non-emissions markets)/
? (USA)
9.0:1 (non-emissions markets)/
8.0:1 (USA)
Valve rocker clearances, cold (intake & exhaust) 0.010 in. (0.254mm) 0.010 in. (0.254mm) 0.010 in. (0.254mm) 0.010 in. (0.254mm) 0.010 in. (0.254mm) 0.010 in. (0.254mm)
Valve timing (with valve rocker clearances identical) Inlet & exhaust valves to be equally open at TDC Inlet & exhaust valves to be equally open at TDC Inlet & exhaust valves to be equally open at TDC Inlet & exhaust valves to be equally open at TDC Inlet: opens 18 BTDC, closes 58 ABDC
Exhaust: opens 58 BBDC, closes 18 ATDC
Inlet: opens 18 BTDC, closes 58 ABDC
Exhaust: opens 58 BBDC, closes 18 ATDC
Oil sump capacity 8 pints Imperial /
9.64 pints USA /
4.5 litres
8 pints Imperial /
9.64 pints USA /
4.5 litres
8 pints Imperial /
9.64 pints USA /
4.5 litres
8 pints Imperial /
9.64 pints USA /
4.5 litres
8 pints Imperial /
9.64 pints USA /
4.5 litres
8 pints Imperial /
9.64 pints USA /
4.5 litres
Mfr rated output, bhp/torque 95 bhp@5000 rpm/
117 ft/lb@3000 rpm
95 bhp@5000 rpm/
117 ft/lb@3000 rpm
104 bhp@5300 rpm/
117 ft/lb@3000 rpm
95 bhp@4700 rpm/
117 ft/lb@3400 rpm
95 bhp@5000 rpm/
117 ft/lb@3400 rpm (USA)
? bhp@5000 rpm/
97 ft/lb@2900 rpm (USA)
Carburettors
  GT-6
(early)
GT-6
(late)
GT-6 Mk2 GT-6+ GT-6 Mk3
(early)
GT-6 Mk3
(late)
Carburettors Stromberg CD 150 Stromberg CD 150 Stromberg CDS 150 Stromberg CDSE 150 Stromberg CDSE 150 Stromberg CDSE 150
Metering needle 6J 6J 6AL B5AJ B5BT non-emissions markets/
B5AJ (early 1971 only, US & Sweden)/
B5CF (late 1971 & after, US & Sweden)
B5CF (all markets)  
Fuel pump
Fuel pump type A.C. mechanically operated, diaphragm type. Glass bowl top A.C. mechanically operated, diaphragm type. Glass bowl top A.C. mechanically operated, diaphragm type. Metal top A.C. mechanically operated, diaphragm type. Metal top A.C. mechanically operated, diaphragm type. Metal top A.C. mechanically operated, diaphragm type. Metal top
Fuel pressure 1.5 to 2.5 psi
(0.106 to 0.176 kg/sq. cm)
1.5 to 2.5 psi
(0.106 to 0.176 kg/sq. cm)
1.5 to 2.5 psi
(0.106 to 0.176 kg/sq. cm)
1.5 to 2.5 psi
(0.106 to 0.176 kg/sq. cm)
1.5 to 2.5 psi
(0.106 to 0.176 kg/sq. cm)
1.5 to 2.5 psi
(0.106 to 0.176 kg/sq. cm)
Ignition system
  GT-6
(early)
GT-6
(late)
GT-6 Mk2 GT-6+ GT-6 Mk3
(early)
GT-6 Mk3
(late)
Coil Lucas HA12 Lucas HA12 Lucas HA12 Lucas HA12 Lucas 16C6 used with ballast resistor Lucas 16C6 used with ballast resistor
Spark plug type Champion N9Y
(3/4" reach by 14mm)
NGK equivalent: BP6ES
Champion N9Y
(3/4" reach by 14mm)
NGK equivalent: BP6ES
AC Delco 42XLS
or
Champion N-9Y
NGK equivalent: BP6ES
AC Delco 44XLS
or
Champion UN12Y
NGK equivalent: BP6ES
Champion N9Y
NGK equivalent: BP6ES
North American cars:
Champion UN12Y
Champion N9Y
NGK equivalent: BP6ES

North American cars:
Champion UN12Y
Spark plug gap 0.025" (0.64mm) 0.025" (0.64mm) 0.025" (0.64mm) 0.025" (0.64mm) 0.025" (0.64mm) 0.025" (0.64mm)
Firing order 1-5-3-6-2-4 1-5-3-6-2-4 1-5-3-6-2-4 1-5-3-6-2-4 1-5-3-6-2-4 1-5-3-6-2-4
Distributor type Delco Remy D202 Delco Remy D202 Delco Remy D204 Delco Remy D204 Delco Remy (Emissions vehicles: D204) Delco Remy (Emissions vehicles: D204)
Distributor contact gap 0.015" (0.38mm) 0.015" (0.38mm) 0.015" (0.38mm)
(Owner's manual has a typo for the mm number)
0.015" (0.4mm) 0.015" (0.4mm) 0.015" (0.4mm)
Distributor rotor rotation anti-clockwise anti-clockwise anti-clockwise anti-clockwise anti-clockwise anti-clockwise
Condenser capacitance (mfd) .20 .20 .20 .20 .20 .20
Dwell angle (degrees) 40 - 42 40 - 42   40 - 42    
Ignition timing Static: Points open 13 BTDC
Idle speed: 600 - 650 rpm
Static: 13 BTDC
Idle speed: 600 - 650 rpm
Static: 10 BTDC Non-emission control vehicles:
Static: 10 BTDC

Emission control vehicles:
Stroboscopic @ idle: 4 ATDC
Idle speed:800 - 850 rpm
Approx. Static: 6 BTDC
Non-emission control vehicles:
Static: 10 BTDC

Emission control vehicles:
Stroboscopic @ idle: 4 ATDC
Idle speed:800 - 850 rpm
Approx. Static: 6 BTDC
Non-emission control vehicles:
Static: 10 BTDC

Emission control vehicles:
Stroboscopic @ idle: 4 ATDC
Idle speed:800 - 850 rpm
Approx. Static: 6 BTDC
Recommended fuel 100 octane (RON)

[If] using fuel having a minimum rating of 97 octane (RON), the static ignition timing should be retarded to 7 BTDC   *
100 octane (RON)

[If] using fuel having a minimum rating of 97 octane (RON), the static ignition timing should be retarded to 7 BTDC   *
  100 octane (RON)

When [...] it is neccessary to use fuels of lower or unknown rating, the ignition timing must be retarded from the specified setting, to prevent audible detonation (pinking), under all operating conditions, otherwise serious damage to the engine may occur.   *
91 octane (RON)   * 91 octane (RON)   *
  GT-6
(early)
GT-6
(late)
GT-6 Mk2 GT-6+ GT-6 Mk3
(early)
GT-6 Mk3
(late)
Cooling system
Type Low-pressure with overflow bottle Low-pressure with overflow bottle Low-pressure with overflow bottle Low-pressure with overflow bottle "No-loss" system with overflow bottle "No-loss" system with overflow bottle
Radiator cap pressure rating 7 lb. 7 lb. 7 lb. 7 lb. 13 lb. 13 lb.

1.3   Transmission & rear axle

1.3.1   Description
1.3.2   Gearbox & rear axle serial numbers
Gearbox & rear axle serial numbers
  GT-6 GT-6 Mk2/+ GT-6 Mk3
Gearbox     (Home) KE1 to ? / (USA) KF 10,001 to ?
Rear axle (cars not equipped with overdrive)     KC 66001 to ?
Rear axle (cars equipped with overdrive)     KD 55001 to ?

1.3.3   Gearbox & rear axle data
Gearbox & rear axle data
  Reverse 1st 2nd 3rd O/D 3rd 4th O/D 4th
Gear ratio 3.10 2.65 1.78 1.25 1.0 1.0 .8
Overall ratio (standard 3.27 differential) 10.15 8.66 5.82 4.11   3.27  
Overall ratio (3.89 differential) 12.06 10.31 6.92 4.86 3.89 3.89 3.11
Gearbox lubricant capacity (dry & excluding overdrive) 1.5 pints (Imperial)/1.8 pints (US)/0.85 litres
Gearbox lubricant capacity (with overdrive) 2 3/8 pints (Imperial)/2.85 pints (US)/1.35 litres
Rear axle lubricant capacity 1 pint (Imperial)/1.2 pints (US)/0.57 litres
Gearbox lubricant GL4 SAE90
Overdrive lubricant GL4 SAE90
Rear axle lubricant GL4 SAE90



1.4   Suspension & steering

1.4.1   Front road spring data
Front road spring data (all models)
Part number 212425
Wire diameter 0.45 +/- 0.002" (11.43+/- 0.05 mm)
Mean coil diameter 3.13 +/- 0.020" (79.5 +/- 0.5 mm)
Number of working coils 9 1/2
Free length 12.46" (316.5 mm)
Fitted length (test length 8.06 +/- 0.09" (204.7 +/- 2.3 mm)
Fitted load (test load) 880 lb. (399.2 kg)



1.5   Brakes

1.5.1   Brake system specifications
Brake data, all models
Manufacturer Girling
Operation Pedal operates all four brakes hydraulically. Handbrake only operates rear brakes via mechanical coupling.
Front wheels, type caliper disc brakes
Front disc diameter 9.7" (246.4 mm)
Front lining area 22.2 sq. in. (143.22 sq. cm)
Front swept area 197 sq. in. (1270.97 sq. cm)
Front caliper bleed nipple thread size 3/8" UNF
Rear wheels, type drum brakes, leading & trailing shoe
Rear shoe lining dimensions 8" x 1 1/4" (203mm x 31.75mm)
Rear lining area 38 sq. in. (245.16 sq. cm)
Rear swept area 63 sq. in. (406.45 sq. cm)

Master & slave cylinder specifications changed through the run of the cars.

Girling Powerstop brake servo (fitted to most late Mk3's) listed as option in parts catalogs, but not in sales catalogs.

Tandem brake system with special master cylinder & separate hydraulic circuits for front & rear in later models.




1.6   Chassis

1.6.1   Dimensions
Dimensions
  GT-6 GT-6 Mk2/GT-6+ GT-6 Mk3
Overall length 12' 1" (368 cm) (145 in.) 147 5/8 in. (375.0 cm) 149 in. (3886 mm)
Width (over handles) 4' 9" (145 cm) (57 in.) 57 in. (144.8 cm) 58 1/2 in. (1488 mm)
Height (unladen) 3' 11" (119 cm) (47 in.) 47 in. (119.5 cm) 47 in. (1195 mm)
Weight, dry (approx., excluding optional equipment) 16 cwt. (813 kg) (1,792 lb.) 17 cwt. (863 kg) (1, 903 lb.) 1936 lb. (878 kg)
Weight, complete (including fuel, oil, water, & tools) 17 cwt. (865 kg) (1,907 lb.) 18 cwt. (914 kg) (2,015 lb.) 2030 lb. (921 kg)
Max. gross vehicle weight 21 cwt. (1067 kg) (2,352 lb.) 22 cwt. (1117 kg) (2,463 lb.) 2525 lb. (1145 kg)
Wheelbase 6' 11" (2110 mm) 83" (211.0 cm) 83" (211.0 cm)
Track, front 4' 1" (1245 mm) 49" (124.5 cm) 49" (124.5 cm)
Track, rear 4' 0" (1220 mm 49" (124.5 cm) 49" (124.5 cm)
Ground clearance (laden) 4" (102 mm) 4" (10.2 cm) 4" (10.0 cm)
Turning circle 25' 3" (7700 mm) 25.25 ft. (7.7 m) 25.3 ft. (7.7 m)
Steering: turns lock-to-lock 4 1/4 4 1/4 4 1/2
Numbers in italics calculated from manufacturer's data

1.6.2   Capacities
Capacities
  GT-6 GT-6 Mk2/GT-6+ GT-6 Mk3
Fuel tank 9.75 gal. (Imperial)/11.7 gal. (US)/44.3 litres 9.75 gal. (Imperial)/11.7 gal. (US)/44.3 litres 8.5 gal. (Imperial)/9.5 gal. (US)/38 litres
Engine sump 8 pints (Imperial)/9.64 pints (US)/4.5 litres 8 pints (Imperial)/9.64 pints (US)/4.5 litres 8 pints (Imperial)/9.64 pints (US)/4.5 litres
Gearbox
(dry & excluding overdrive)
1.5 pints (Imperial)/1.8 pints (US)/0.85 litres 1.5 pints (Imperial)/1.8 pints (US)/0.85 litres 1.5 pints (Imperial)/1.8 pints (US)/0.85 litres
Gearbox
(with overdrive)
2 3/8 pints (Imperial)/2.85 pints (US)/1.35 litres 2 3/8 pints (Imperial)/2.85 pints (US)/1.35 litres 2 3/8 pints (Imperial)/2.85 pints (US)/1.35 litres
Rear axle 1 pint (Imperial)/1.2 pints (US)/0.57 litres 1 pint (Imperial)/1.2 pints (US)/0.57 litres 1 pint (Imperial)/1.2 pints (US)/0.57 litres
Cooling system
(with heater & water bottle)
11 pints (Imperial)/13.2 pints (US)/6.2 litres 11 pints (Imperial)/13.2 pints (US)/6.2 litres 11 pints (Imperial)/13.2 pints (US)/6.2 litres


1.6.3   Chassis serial numbers
Chassis serial numbers by model year
Mk1 KC 1 through KC 6539 1967
Mk1 KC 6540 through KC 49,999 1968
Mk2/+ KC 50,000 through KC 74,999 1969
Mk2/+ KC 75,000 & up 1970
Mk3 KF 1 through KF 10,000 1971
Mk3 KF 10,001 through KF 20,000 1972
Mk3 KF 20,001 & up 1973



1.7   Production changes

The difference in the production year & the model year is important to understand. For example, cars built, advertised, & sold as 1972 Triumph models actually began production in 1971 & continued production into 1972. A car built in December 1971 would be a 1971 production year car, & a 1972 model year car. Changes at chassis numbers are more definite references, but are not always available.

Some changes to the engine are referenced to the engine number.

A partial list of production changes is below:
Production changes
Production date Model year     Model     Chassis number Engine number Change
October, 1966   GT-6     GT-6 production car introduced
    GT-6   KC 5,001 Engine block changed from design with removable pushrod tubes to design with pushrod passages cast integral with the block
1968   GT-6 Mk2/
GT-6+
    GT-6 Mk2/GT-6+ introduced
Swing-axle rear suspension discontinued, rotoflex rear suspension standard
Chrome-bezel instruments discontinued, black-bezel gauges standard
1969   GT-6 Mk2/
GT-6+
    Reclining seats standard
New design steering wheel
  1970 GT-6+     Black-painted windshield frame & white coach stripe standard
1970 1971 GT-6 Mk3     GT-6 Mk3 introduced for 1971 model year
Body redesign
Cooling system changed to 13 lb. "no-loss" design
Silver-painted oval-hole steel wheels standard
  1972 GT-6 Mk3     US cars: Optional anodized aluminum wheel trim rings option available, optional dealer-applied gold stripe kit available
    GT-6 Mk3   KE/KF/KG 10,000 Engine block changed to recessed cylinder bore design
    GT-6 Mk3 KE/KF 12,391   Front brake calipers changed from Girling Type 16PB to Girling Type 16PB Metric; mounting bolts & pads also changed
1973   GT-6 Mk3 KE/KF 20,001   Rotoflex rear suspension discontinued, 'Swing Spring' rear suspension standard; change revises rear spring & attachments to differential, axle shafts, vertical links, dampers, hubs, trailing arms & attachments, etc.
Rear brakes revised with all new hydraulic cylinders, brake drums, back plates, springs, shoes, etc.
November, 1973   GT-6 Mk3     Last GT-6 rolls off the assembly line



1.8   Optional equipment

1.8.1   Racing wheels (USA)
USA showroom brochures listed as options SCCA-approved racing wheels of aluminum or magnesium. These wheels were not manufactured by Triumph, but provided through the dealer.

The wheels were the Silverstone model from American Racing, available in magnesium or aluminum. Magnesium is the more common. You didn't typically see them with the absurd three ear spinner!

I have six of them but they're not suitable for racing! The magnesium over time weakens with internal corrosion. Buy modern Panasports for the look.

- thanks to Steve Smith

1.8.2   Air conditioning (USA)
By the 1970s, it was common in warmer sections of the USA to see in the Triumph dealer showrooms cars with what looked like factory-installed air conditioning. These air conditioning units were in fact installed by the dealership, as customer expectation of air conditioning in cars became general about this time. Most of the units were bought from a single aftermarket supplier which manufactured model-specific air conditioning for many makes of cars which did not originally have air conditioning.

Most of these systems were later removed by owners. Removal usually occurred when the units needed repair or recharging, as the benefit of the air conditioning system was weighed. The system didn't do much to mitigate the famous GT6 cabin heat, especially on the warmest days when it was needed most, and the penalty to performance resulting from driving the air conditioning compressor often seemed worth eliminating in the lower-power late US-spec GT6 engines. Removal of the components would additionally improve performance by saving weight.

The original kit & installation comprised: The simple system would likely be more effective if used today, incorporating typical more efficient modern components & approaches such as improved cabin insulation, more-efficient compressors, lightweight bracket for idler pulley & compressor, & a typical A/C vacuum switch to disengage the air conditioner compressor's clutch on acceleration.



TRIUMPH GT-6