Hillman Imp cars (also Sunbeam Stilleto, Singer Chamois, Husky Estate, Asp, and Commer Imp Van)

by Keith Adams

The Hillman Imp's beginnings date back to 1955; the 1-litre class had sizeable sales in the UK, and Rootes had no cars in that part of the market. Michael Parks (project engineer - who later went on to work for the Ferrari F1 team) and Tim Fry (co-ordinating engineer) were given a clean sheet of paper and responsibility for pushing the new car through. Fry and Parkes thought that the new car should reach these goals:

• Room for two adults and two children.
• At least 60mph maximum speed and 60mpg fuel economy.
• Echoing competitors, a rear engine layout.
• The car should be fun to drive.

The UK’s first gas rationing since World War II, as a result of the 1956 Arab destruction of a Syrian oil pipeline, put more pressure on Rootes to move forward, especially as German “bubble cars” started to sell in quantity despite poor driving dynamics and safety; they managed to get 40 miles per gallon.

The Slug appears

According to Graham Robson, the project progressed “without much impetus” towards a 2+2 air-cooled economy car. The team soon came up with a highly aerodynamically styled economy saloon named "the slug," powered by the Villiers flat-twin engine. All its design objectives would have been met with this car, Rootes board members made it clear they were not allowing Rootes Group to produce a car which such resemblance to the German "bubble cars." The board also made it clear that it did not want to see the Rootes Group name compromised by selling an "austerity" car, intelligent engineering or not. Allegedly, Lord Rootes hated the sight of it so much, he refused to ride in it!

The board concluded that Rootes needed a small car, but it needed to maintain the quality and solidity of the rest of the Rootes range. It needed a four cylinder engine, and had to accommodate four adults. From this desire to create a bigger, better mini car, Project Apex was thus created; and Technical Director Peter Ware saw it to maturity.

The Apex prototypes

The stage two Slug prototype still looked rather utilitarian, but it was a step towards the Apex; after this, all would change.

Rootes had no small car engine, and approached local company Coventry Climax, which made the FWMA all-aluminium racing engine. Tim Fry contacted them and asked if it were possible to get hold of installation drawings, telling them that he was in the process of developing a car that could be an ideal beneficiary. Coventry Climax were happy to co-operate, and as a result, Fry put the tiny engine and gearbox into one of the prototypes, named "Little Jim."

The Coventry Climax engine was developed into something far more suitable for road use: it was expanded to 875cc, detuned to 39bhp, and most of its internals were changed in favour of longer life items. Even in production specification, the engine was a peach, and was more advanced than its immediate rivals, with an overhead camshaft and lightweight construction.

The "clean sheet" approach also extended to the gearbox: one of the problems encountered during Apex development was that there had been numerous gearbox failures. No doubt, this was due to the "revvy" nature of the Coventry Climax engine, which demanded frequent gear changes. It was decided that the new car would sport a transaxle (gearbox and differential in the same housing), but because Rootes had never used this arrangement in any other cars, it hired Adrian West as Senior Transmission Engineer. West's task was to design and build a transaxle that was strong enough to withstand enthusiastic use, yet be light enough to appeal to all buyers the car was aimed at.

West had wide experience of gearbox design at Simca, Renault, and Fiat. He achieved the goals handsomely, and the transaxle he produced boasted fantastic change quality, largely attributable to the use of a baulk-ring synchromesh (something the Mini missed out on at its launch, and suffered from as a result). The combination of Coventry Climax engine and West transaxle was hard to beat; and it was years ahead of the opposition when the Imp was launched in 1963.

The engine/gearbox might have been a success, but there were questions about the styling. After Peter Ware had ditched the aerodynamic styling of the original prototypes, Apex was quickly moved forwards. Keen to project a more youthful image, Bob Saward's styling department looked across the pond to the USA for styling influences. The original three-box Imp prototypes were rather bland looking cars, and it was only when the addition of "Americana" took place, that the essential character of the car came bursting through. The Chevrolet Corvair was its model, since it was popular with the young at the time.

The decision to retain a rear-engined layout took a while to make. In 1955, many continental rivals slung their engines out back, but in the UK, the small car opposition had stubbornly remained with the classic front engine/rear drive layout. The UK's motoring press began to see the conventional products produced by the Rootes Group as being boring, and stung by such (gentle) criticism, the company wanted to produce something totally "Continental" in its approach. However, in 1959, Alec Issigonis turned the world upside down by proving that front engine/front wheel drive was the future for small cars. The Mini may have taken time to gain acceptance with the buying public, but engineers and designers knew that the rear engined family car had been rendered obsolete.

By that time, the Apex had grown up, and the rear engined layout was now carved in stone. To go front engined at this point would mean scrapping the project up to that point and starting again, and given Rootes' ambitions of expansion, a launch that took place sooner rather than later was desired.

By the late-1950s, Rootes felt that expansion was the only way to survive. Given that each new Apex sold would be a new customer to Rootes, extra production would be needed. However, the British government made it plain that if Rootes wanted to expand using government assistance, it would need to do so in an enterprise area. This struck quite a blow for the future plans of Rootes, because it had already been refused permission to develop Ryton, and now it would be forced to set up a new plant away from its Coventry heartland. The pressure exerted on Rootes led the company to Linwood, near Glasgow, and it would be here that a new factory would be built thanks to a government loan, and in it, the new car would be built.

Production of the Apex might have presented problems, but there were also issues that befell its development. The Apex engineering team was based in Ryton, and was treated as an entirely different entity to the main engineering office at Stoke. As the Apex programme had dragged considerably, it was also treated to an injection of haste towards the end, which meant that several exciting features that the engineers wanted to hone to perfection (such as the pneumatic throttle, automatic choke and marginal cooling) were never tested fully. Ware knew the dangers of launching a car without thorough development, and in the fullness of time, he was proved correct.

Graham Robson also relates that the Apex was committed to production far too early, and this was probably down to the fact that Rootes wanted no further delays, or a newly opened factory which would be standing idle at the point it was to be declared open in May 1963.

The Imp appears

Details of the upcoming car were scooped in the first issue of Small Car magazine (which later became CAR) in 1962. The remarkably accurate article prepared us for a rear-engined mini-Rootes, although calling it "Ajax" was adrift. The idea of a mini-Rootes took some getting used to, and even though the company were clearly going to call it "Imp" and restrict it to the "Hillman" marque, it was still positioned a long way below anything else in the then current range.

The motoring press were largely favourable about the Imp, although comparisons with the Mini were always going to prove difficult to avoid. Nevertheless, the Imp's superb engine, gearbox and handling were praised in equal measure. The MOTOR magazine in its road test of May 8th 1963 were very enthusiastic:

Handling: The fact remains, however, that the Imp can be hurled into corners at speeds which would be suicidal with most saloons and with very little roll and no tyre squeal it just motors round them. It is so close to being a neutral steering car that different driving techniques can tip the balance one way or the other.

Transmission: The gearchange, as we have said is quite certainly one of the best, if not the best we have ever handled.

Performance: For an 875cc car, the performance is astonishingly lively and bears comparison with many family saloons up to 1600cc.

Although it was rear engined, the addition of that lift-up rear screen (do not get carried away and describe it as a "hatchback") meant that the Imp's practicality was also praised. Motor was forthright in its verdict too, and were most optimistic about the Imp's future: "If Rootes cannot sell 150,000 Imps a year, as they have planned, we shall eat our editorial hat." Sometimes hindsight can be a wonderful thing. It soon became clear that the Imp's rushed final development phase would have a lasting impact on the small car's reputation with customers.

Problems that would have been picked up in those late development months soon manifested themselves: defective water pumps and automatic chokes, overheating, water leaks, throttle problems and lack of performance. These soon became widely known in the trade and with buyers, and a poor reputation for reliability - so easily won - would never be shaken off. Rootes dealers were ill-equipped to deal with such problems, and at the production stage, it took years to iron them out. Linwood's industrial relations were poor from day one, so any running changes that needed introducing were drip-fed rather than rushed in.

John Simister's retrospective Motor article from 1986 noted some of the issues: "...the cylinder blocks for the die cast engine were cast in Linwood but had to be sent down to Coventry for machining and assembly and returned to Scotland for installation." It was madness, and was repeated with Avenger assembly.

But had the Imp gamble paid off? Arguably, its 1963 launch date was too late for another mini-car; the petrol crisis had passed and the economy was booming. Small car sales were still strong, but the Imp was already below the UK car maket's centre of gravity. The rear-engined layout was also now seen as past its prime, thanks to BMC's front wheel drive exploits.

The year after the Hillman Imp was launched, Rootes Group was forced to accept its first parcel of cash from Chrysler, thanks to mounting losses caused by disappointing Imp sales and the huge Linwood investment. Linwood could not produce the Imp efficiently at anywhere near projected volumes, as its engine and gearbox were extremely labour intensive to produce.

Losses continued, and Chrysler's takeover of the Rootes Group followed in 1967.

The Hillman Imp expands into other brands

Even though the Imp was clearly defined as a Hillman at the time of its launch, it soon became apparent that the policy of badge engineering would need to be followed in order to maximise sales potential. In short order coupé, van, estate car versions became available, and plusher Sunbeam- and Singer-badged versions were phased in. It was never going to be enough, though. By the time Chrysler was fully in charge of the company, it was clear that any further meaningful development of the Imp was never going to happen.

Imp marque and model variations

Facelifts were investigated and then dropped; as were larger engined derivatives. Rootes had now become known as Chrysler UK, although the structure of the company remained largely in place. This would not last long into the 1970s, and the process of rationalisation explains why Ryton's front wheel drive supermini projects never proceeded very far from the stylists' sketch boards.

The Imp marked something of a dead-end in the company's history, and even though it was eventually turned into a reliable car that handled and performed well, it was never taken on by Chrysler and developed to face the challenge of the 1970s. Certainly, the rear engined layout played against it from day one, but that did not mean that its excellent engine and gearbox could be utilised in any other installation. It is fair to say that the Coventry Climax engine was expensive and labour intensive to build, but surely some of its nicer features could be used elsewhere.

Chrysler saw it another way, and refused to kill it or develop it. The vastly simpler Avenger was also built at Linwood, but it was not a replacement for the Imp, and so, the little car remained in production until the Sunbeam replaced it. This likeable small car did not owe anything at all to the Imp (or its front wheel drive design studies) apart from the slant-four engine in the 928cc version, which was a development of the Coventry Climax engine. However, by the mid-1970s, Chrysler's European arm was deep in crisis, a wider product strategy demanded a different solution.

Ultimately, the Imp (like the Neon, Volare, and 1957 Chrysler Corporation lines) was a victim of the oft-repeated mistake of launching a car before it had been fully developed. Reputations are hard earned and easily lost...

The Imp Asp

Rootes' engineers knew that the Imp chassis was capable of handling more power, and decided to work on a sporting variant. Using the existing alloy overhead-cam engine, tuned for performance, and using a pretty (Tim Fry, along with Bob Saward and Ron Wisdom, styled) body, the engineers stirred the pot to produce the Asp.

Rootes approached Jensen Motors and asked them to study the feasibility of producing the Asp for them, at the rate of 500 units per week. The plans would have centred around a steel bodied car, which would have used the standard 875cc engine, with the option of a more highly tuned 998cc variant. The car certainly had potential, and cannily, Rootes planned for the fall-back of glass fibre construction, had steel proved too costly.

Sadly, the Asp project was dropped through lack of resources — Chrysler had yet to inject its cash into Rootes.