Triumph Stag
The Triumph Stag is a 2+2 sports tourer which was sold between 1970 and 1978 by the British Triumph Motor Company, styled by Italian designer Giovanni Michelotti.
Design and styling
Envisioned as a luxury sports car, the Stag was designed to compete directly with the Mercedes-Benz SL class models. All Stags were four-seater convertible coupés, but for structural rigidity – and to meet proposed American rollover standards of the time – the Stag required a B-pillar "roll bar" hoop connected to the windscreen frame by a T-bar. A body-colour removable hard top with defrost wires on the rear window, full headliner and lever operated quarter windows was a popular factory option.The car started as a styling experiment cut and shaped from a 1963–64 pre-production 2000 saloon, also styled by Giovanni Michelotti. His agreement was, if Harry Webster, Director of Engineering at Triumph, liked the design, Triumph could use the prototype as the basis for a new model. Webster loved the design and took the prototype back to England. The result, a two-door drophead, had little in common with the styling of its progenitor 2000, but retained the suspension and drive line. Triumph liked the Michelotti design so much that they propagated the styling lines of the Stag into the new T2000/T2500 Mark II saloon and estate model lines of the 1970s.
Triumph gave new projects four-letter development code names and the Stag was the only Triumph to take its development code name into production.
Engineering
The initial Stag design used the saloon's 2.0-litre six cylinder engine which was intended to be uprated to 2.5-litres for production cars, but Webster intended the Stag, large saloons and estate cars to use a new Triumph-designed overhead cam 2.5-litre fuel injected V8. In 1968, under the direction of Engineering Director Harry Webster and his successor as Chief Engineer, Spen King, the new 2.5 PI V8 was enlarged to to increase the power available. To meet emission standards in the US, a key target market, the troublesome mechanical fuel injection was dropped in favour of dual Zenith-Stromberg 175 CDSE carburettors. In common with several other manufacturers, a key aim of Triumph's engineering strategy at the time was to create a family of in-line and V engines of different size around a common crankshaft. The various configurations Triumph envisaged would enable the production of four-, six-, and eight-cylinder power plants of capacity between 1.5 and 4 litres, sharing many parts, and hence offering economies of manufacturing scale and of mechanic training. A number of iterations of Triumph's design went into production, notably a 2.0-litre slant four-cylinder engine used in the later Dolomite and TR7, and a variant manufactured by StanPart that was initially used in the Saab 99. In 1968 the Saab variant became the first of these engines to be fitted to a production car, followed by the Stag V8 in 1970. Sometimes described as two four-cylinder engines siamesed together, it is more strictly correct to say the four-cylinder versions were the left half of a Stag engine.It has sometimes been alleged Triumph was instructed to use the all-aluminium Rover V8, originally designed by Buick and under development by Rover at the time, but claimed it would not "fit". Installation testing of both the Triumph V8 and the Rover V8 was carried out in May/June 1967, the conclusion being that the engine was too tall and that front structure changes would be necessary. It was decided not to further hold up Stag development and to proceed with the Triumph V8 unit. Although later enthusiasts have shown that it can be made to fit the space, the decision to go with the Triumph V8 was probably more due to the Buick's lack of British sales experience, the fact that there was not a manual gearbox offered by Rover at the time, and that the different torque characteristics and weight would have entailed substantial re-engineering of the Stag when it was already behind schedule. Such a substitution would also have required a rethinking of the wider engineering strategy, both of which were important "fit" considerations beyond the comparatively trivial matter of the relative dimensions of the two engines. Furthermore, Rover, also owned by Leyland Motor Corporation at the time, could not necessarily have supplied the numbers of V8 engines required to match the anticipated production of the Stag.
As in the 2000 model line, unitary construction was employed, as was fully independent suspension: MacPherson struts in front, semi-trailing arms at the rear. Braking was by front disc and rear drum brakes, while steering was power-assisted rack and pinion.
Production
The car was launched nearly two years late in June 1970, to a warm welcome at the international auto shows. In the UK the Stag was an immediate success for Triumph with a 12-month waiting list rapidly being established and cars changing hands at well above list price, but when it was released into the US, its main target market, it rapidly acquired a reputation for mechanical unreliability, usually in the form of overheating. These problems arose from a variety of causes.First, the collaboration with Saab on the related slant 4 engine gave rise to design features being carried over to the V8, some of them questionable from an engineering perspective. For example, because the Saab 99 placed the engine back to front in the engine bay, the traditional mounting of the water pump on the front face was not possible. The answer for the Saab engine was to place the water pump within the top of the engine block, which is a higher position than is usual. Due to the use of a common machining line for both the slant 4 and the V8, this positioning was copied to the V8. If the engine became hot in traffic, and coolant escaped from the cooling system via the expansion bottle, the volume of fluid left when the engine cooled down again fell. If this was not noticed and it continued to occur, the coolant level would eventually fall below that of the pump, which would be unable to circulate the coolant. Overheating would result, often accompanied by pump failure. Water pump failures also sometimes occurred due to poorly-hardened drive gears, which wore out prematurely and stopped the water pump. Once this key component of the cooling system had failed, overheating ensued.
A second cause of engine trouble was the lack of attention to corrosion inhibitor in the coolant. The block was made from iron and the heads from aluminium, a combination that required the use of corrosion-inhibiting antifreeze all year round. This point was not widely appreciated by owners or by the dealer network supporting them. Consequently, engines were affected by electrolytic corrosion, and white alloy oxide sludge collected in radiator cores, reducing radiator efficiency and again causing overheating. The result was head gasket failure due to cylinder head heat distortion, a very expensive repair. Owners would usually get their repaired cars back with the radiator still clogged, leading to repeat failures.
A third cause of trouble was the engine's use of long, simplex roller link chains, which would first stretch and then often fail inside fewer than, resulting in expensive damage. Even before failing, a stretched timing chain would skip links and cause valves to lift and fall in the wrong sequence, so that valves hit pistons and damaged both. This fault may have been worsened by poor quality chains.
Another problem with the cylinder heads was said to be the arrangement of cylinder head fixing studs, half of which were vertical and the other half of which were at an angle. Anecdotally, this arrangement was used to reduce production costs, as the cylinder head mounting studs and bolt were all accessible with the rocker covers fitted. This allowed the factory to assemble the cylinder head completely before fitting to the engine. This arrangement worked well enough on the 4-cylinder engines, but in the V8 the angled and vertical studs, when heated and cooled, expanded and contracted in different directions sufficiently to give rise to sideways forces that caused warping of the engine block. The problem was made worse by the engine's propensity to overheat.
Finally, although pre-production engines were built meticulously, those fitted to production cars were not subject to the same careful quality control. Engines are still being discovered with casting sand and core wire inside, blocking the coolant passages and causing overheating.
This combination of manufacturing and maintenance flaws led to some engine failures in the UK but in the US the situation was exacerbated by the need to fit low compression pistons to comply with California's low octane petrol requirements, and the associated advance in ignition timing to meet that country's continually changing emission regulations. The result was that the engine developed greater heat and, when automatic transmission and air conditioning were fitted, the engine cooling ability was overly compromised. Although US cars were fitted with engine cowls to try to compensate, all too often the result of a freeway tailback was an overheating engine. Time magazine rated the Triumph Stag as one of the 50 worst cars ever made.
British Leyland never materially re-engineered the Triumph 3.0 litre OHC V8 to address these issues, other than introducing a domed piston to aid combustion and a high-pressure cooling system that boiled over at a higher temperature. Another problem was that the Stag was always a relatively rare car. British Leyland had around 2,500 UK dealers when the Stag was on sale and a total of around 19,000 were sold in the UK over seven years. Thus the average dealer sold only seven or eight Stags during the car's production run, or roughly one car per year. This meant that few dealers saw defective Stags often enough to recognise and diagnose the cause of the various problems.
A number of owners replaced the troublesome engine with units from other cars, such as the Rover V8, or the Triumph 2.5-litre engine around which the Stag was originally designed. The number of such conversions undertaken is not known, but as at September 2024, fewer than 6% of surviving Stags known to DVLA have a 3.5-litre engine or larger, according to www.howmanyleft.com., while 92% have a 3-litre engine. It is not clear how many of these are original 3-litre Stag engines and how many are Ford Essex units. It is thought by the relevant owners club that the Ford engine powers fewer Stags than does the Rover V8.
The last production Stag is kept at the Heritage Motor Centre, Warwickshire.