Sunbeam Sport

Rootes Group

Industry	Automotive
Founded	1909
Fate	Taken over by Chrysler Europe in 1967
Headquarters	United Kingdom
Products	Automobiles, including Hillman Imp

Hillman Imp

The Hillman Imp was a compact economy automobile manufactured by the Rootes Group and subsequently Chrysler Europe between 1963 and 1976. Introduced on 3 May 1963, it marked the first instance of a British mass-produced vehicle featuring an aluminium engine block and cylinder head.

Conceived by designers Mike Parkes (who later pursued a career in Formula One) and Tim Fry, the Imp was assembled at the dedicated Linwood facility in Scotland. The lineup extended beyond the Hillman saloon to include an estate version known as the Hillman Husky, as well as van and coupé variants.

The Imp garnered moderate acclaim in both club-level and international rally competitions. In 1964, Rootes launched the Rally Imp homologation model equipped with a larger 998 cc engine. Notably, factory-backed Imps secured first and second places at the 1965 Tulip Rally.

Despite its innovative features, the Imp suffered from reliability problems that undermined its market standing and played a role in Rootes Group’s takeover by Chrysler Europe in 1967. Production ceased in March 1976 after nearly 500,000 units had been built over a 13-year span.

Development

Internally designated as the APEX project, the Imp was conceived in reaction to the 1956 Suez Crisis and consequent fuel shortages. With petrol rationing imposed in the UK and dwindling sales of Rootes Group’s larger vehicles, demand grew for small, fuel-efficient cars. The BMC Mini had already dominated this segment since its 1959 launch. Although development began in 1955, focus soon shifted toward creating Rootes’ inaugural compact economical car.

Design leadership was provided by Mike Parkes and Tim Fry: "Mike Parkes and I were close friends. We approached B. B. Winter, director of engineering, proposing to design exactly the car we envisioned. He responded: 'Very well, proceed then!'". Initial concepts included "The Slug," which resembled a bubble car; however, Rootes’ board dismissed this design in favor of something more practical.

Testing was conducted across varied environments—from Norway’s harsh winters to East Africa’s hot summers and Canada’s Arctic conditions—under the supervision of Chief Development Engineer Ken Sharpe.

Rootes had previously experimented with small cars through prototypes such as the 1938–1939 Little Jim, featuring a front-engine configuration with a 750cc power unit, and the post-war 1949 rear-engined Little Jimmy prototype utilizing a Volkswagen-derived twin-cylinder engine. Nonetheless, these earlier models had minimal influence on the Imp’s final design.

The Imp employed a 742cc engine inspired by the Coventry Climax FWMA, originally planned to be available in three displacements: 800cc, 875cc, and 998cc. Due to production expenses, increased vehicle weight, and issues with unreliable dry-liner 998cc units, only the 875cc version reached standard production. This limitation to a single engine size placed the Imp at a disadvantage relative to competitors like the Mini. A taller engine block with an extended stroke was considered but rejected for cost reasons unless market success justified it. Some long-stroke engines were produced and subsequently bored out to 1150cc for competition use by drivers including Paul Emery and Andy Dawson.

Later Rallye Imp models featured costly wet-liner 998cc engines primarily intended for racing rather than everyday driving. It was eventually determined that the dependable maximum displacement for the original 875cc engine was approximately 948cc; however, neither this nor a proposed 928cc variant—planned for a Mark III version of the Imp—were brought into production due to Chrysler’s cost-cutting policies. The concept of a 928cc engine later reemerged in the Chrysler Sunbeam model.

Mark I Imp: 1963–1965

The Hillman Imp was officially introduced on 2 May 1963, with the Linwood factory inauguration conducted by HRH Duke of Edinburgh. Among the earliest produced Imps, one is exhibited at the Glasgow Museum of Transport, while another early 1963 example is preserved at the National Motor Museum, Beaulieu.

Prior to its release, the Imp garnered considerable attention from automotive journalists due to its all-aluminium, water-cooled rear-mounted engine. The Daily Express described it as "the first baby car ever built by the Rootes Group". At launch, pricing was competitive, with the standard version costing £508 and the deluxe model priced at £532.

The name "Imp" originated from Ailsa Craig Ltd., a marine engine manufacturer acquired by Warsop Fram Group in 1962. Rootes Group secured the rights to the name through a trade involving a new Humber Super Snipe. This branding highlighted the vehicle’s compact dimensions and positioned it as a rival to the Mini.

Under the bonnet, the Imp featured a sophisticated water-cooled aluminium overhead camshaft four-cylinder engine inspired by the Coventry Climax FWMA design. This was paired with an aluminium transaxle equipped with full synchromesh—a notable advancement since fully synchronized forward gears were uncommon at that time. The engine was inclined at a 45° angle to lower the center of gravity and enhance handling performance.

To counteract typical oversteer associated with rear-engine layouts, the Imp utilized a semi-trailing arm independent rear suspension—a complex and expensive solution rarely found in small cars during that era. Initially, swing axle geometry was employed at the front, which caused understeer; this issue was mitigated by adjusting camber through lowering pivot points.

Sales within the UK expanded from approximately 33,000 units in 1963 to 50,142 in 1964, but dropped to 42,663 in 1965 due to reliability problems primarily related to inadequate engine cooling. This downturn raised concerns for Rootes as they contended with the Mini, which sold over 1.19 million units throughout that decade.

The Mark I was available as a two-door saloon offered in Basic and De Luxe trim levels. In October 1964, a premium Singer Chamois version was introduced.

Mark II Imp: 1965–1968

In response to early challenges faced by the Mark I, Rootes Group reissued the Imp featuring substantial mechanical and aesthetic improvements. The Mk II replaced the pneumatic throttle linkage and automatic choke with conventional mechanisms, refined front suspension geometry, and implemented updated trim details. Significant upgrades included adding a water pump, enlarging cylinder head ports and valves, and introducing 'Mark II' door badges.

Mark III Imp: 1968–1976

Although never formally designated as "Mark III," the Imp underwent modifications following Rootes Group’s acquisition by Chrysler Europe in 1968, leading to its unofficial label as the "Chrysler Imp." These revisions involved redesigned instrument clusters and steering wheels, replacing the prominent central speedometer with a horizontal arrangement of four round gauges. Additionally, a single multifunction stalk replaced previous dual control levers. While these alterations aligned with wider production streamlining efforts, some critics regarded them as missed chances considering the earlier model’s well-regarded ergonomic design.

Rootes, Chrysler, and the End of Production

Early quality issues harmed the Imp's market standing, causing its sales to peak prematurely before declining, despite attractive pricing, distinctive design, and economical running costs. Misconceptions regarding the upkeep of its alloy engine and frequent failures of the Giubo coupling further damaged its reputation for reliability. Consequently, the Imp was eclipsed by rivals such as the Mini.

The significant capital invested in both the Imp and the Linwood manufacturing facility was a factor in Rootes Group's financial difficulties. While labor disputes and the partnership with Chrysler USA were major contributors to losses, the Imp's disappointing commercial results also played a notable role. Following Lord William Rootes' invitation to Chrysler in 1964, Chrysler took full control of Rootes by 1967. In 1968, prices for most Imp variants were reduced by over four percent despite ongoing inflationary pressures.

Responsibility for the Imp’s withdrawal from production in March 1976—after fewer than 441,000 units had been made—is frequently attributed to Chrysler’s management. The broader failure of Chrysler Europe culminated in its acquisition by Peugeot two years later. The Imp nonetheless remained one of the United Kingdom’s longest-produced models with a production span of 13 years. Its replacement within Chrysler UK’s portfolio was the Chrysler Sunbeam hatchback, which shared its underpinnings with the Hillman Avenger; both vehicles were assembled at Linwood until the factory’s closure in 1981 after an 18-year operation.

Meanwhile, production at the Ryton plant persisted until December 2006, when Peugeot shifted manufacturing to Slovakia.

Design

Developed as a direct rival to BMC’s Mini, the Imp utilized a compact rear-engine, rear-wheel-drive configuration designed to optimize passenger and luggage space both front and rear. It featured an innovative rear hatch that opened to allow access to luggage stored behind the back seat.

This model was Britain’s first mass-produced car with a rear-mounted engine and introduced the use of a diaphragm spring clutch. Its baulk-ring synchromesh transaxle enhanced gear shifting smoothness, overcoming problems that had plagued early Mini transmissions.

The design incorporated several unusual features for its time, including a foldable rear bench seat, an automatic choke—which was uncommon outside North America until the 1970s—and instrumentation displaying temperature, voltage, and oil pressure, rather than relying solely on warning lights as many contemporary cars did since the 1950s.

Powered by an overhead camshaft engine that allowed superior airflow compared to typical OHV units, it was also easily tuned for enhanced performance through upgraded silencers and carburettors. However, modifications made by Rootes for large-scale production rendered this engine less robust than its Coventry Climax predecessor. The Imp employed a variant of the Climax FWMA engine; in contrast, Lotus vehicles used an FWMC engine featuring a different cylinder head design.

Marketing

Initially targeted by Rootes as a secondary vehicle for well-off families, the Imp was promoted as a premium small car equipped with advanced features. Over time, its positioning shifted toward an ultra-budget economy model incorporating some cost-saving design compromises reminiscent of Eastern European brands such as Škoda and later Lada. At one stage, the basic Hillman Imp became the most affordable new car available on the British market, temporarily stimulating sales growth.

Variants and Badge Engineering

Throughout the Imp’s production run, Rootes (which later became Chrysler UK) offered four distinct body styles. The initial saloon model, produced from May 1963 until 1976, included a rear window that could be opened to facilitate loading luggage behind the fold-down rear seat—an uncommon feature for compact cars at that time. In 1965, a van variant named the "Commer Imp" was launched. Two years later, in 1967, the coupe version called the Imp Californian was introduced alongside an estate car derived from van chassis, marketed as the Hillman Husky. Although prototypes of estates based on extended saloon bodies were developed, they never reached the market; customers were limited to the van-based estate with its unconventional design. Production of both van and estate models ceased in 1970.

To broaden market appeal amid sales figures that fell well short of the intended annual target of 100,000 units, several badge-engineered models were introduced. These included the upscale Singer Chamois, launched in October 1964, and the sportier Sunbeam Sport in October 1966, featuring twin-carburettor engines. In many export markets, Singer versions were sold under the Sunbeam brand until Chrysler UK discontinued Singer in May 1970. In certain countries such as France, "Sunbeam" served as the badge for all British Rootes vehicles, including the Imp and Husky.

The coupe’s design closely mirrored the saloon but featured a more steeply angled windscreen and a fixed rear window. Although its sportier appearance was unveiled at the Paris Motor Show in October 1967 with the Sunbeam Stiletto model, it did not provide any performance benefits over the saloon, which actually had slightly superior aerodynamic qualities. This coupe body style was also used for less powerful Hillman Imp Californian and higher-end Singer Chamois variants.

Manufacture

The Imp represented a major and expensive gamble for Rootes, which had limited recent experience producing small cars despite originally launching the compact Hillman Minx back in 1931. By the time of the Imp's debut, however, the Minx had transitioned into a medium-sized family vehicle. The Imp was pioneering in its use of an aluminium engine block within mass production—a complex undertaking that involved far more than simply replacing cast iron with aluminium components. This innovation necessitated building a new assembly plant equipped with computerized systems in Linwood, Renfrewshire. The UK Government provided Regional Assistance grants to support this investment aimed at creating approximately 6,000 jobs in a region suffering economic decline due to shrinking shipbuilding industries.

The facility included an advanced die-casting operation dedicated to aluminium engine casings and involved acquiring a stake in a new Pressed Steel Company plant responsible for manufacturing body panels. However, Linwood’s location posed logistical difficulties since it was situated more than from Rootes’ primary Ryton-on-Dunsmore factory. Engine castings were transported to Ryton for machining before being returned to Linwood for final assembly—a journey amounting to a round trip. Managing this required intricate train schedules moving parts and completed vehicles back and forth. To improve logistical efficiency, Linwood also produced body pressings for the Hillman Avenger model, which were then shipped south to Ryton.

The workforce recruited locally—predominantly from shipbuilding backgrounds—lacked specialized skills in automobile assembly, which negatively impacted both build quality and reliability of the Imp. Furthermore, ongoing industrial disputes and frequent strikes throughout the 1960s and 1970s caused regular interruptions to production.

In total, around half a million Imps were manufactured, with roughly half of these produced during the initial three years of production.

Overseas assembly

Complete knock down (CKD) kits were shipped abroad for assembly in countries including Australia, Costa Rica, Ireland, Malaysia, Malta, New Zealand, the Philippines, Portugal, South Africa, Uruguay, and Venezuela. In New Zealand, Todd Motors assembled Hillman vehicles from around 1964 until 1970, ceasing Imp production to focus on manufacturing the Hillman Avenger. Todd Motors operated two assembly lines at Petone, which were shared between the Avenger/Hunter and Chrysler Valiant models.

In Australia, Rootes Australia began assembling Imps at their Port Melbourne facility starting in 1964. The models produced there included:

• PM Imp: Offered only in Standard trim (1964–65), assembled from UK Mk I CKD kits. The Super Imp variant was introduced in 1965, featuring enhancements later incorporated into subsequent models.
• PA Imp ("IMP II"): Available in Standard or Super trim (February 1966–March 1968), still utilizing UK Mk I CKD kits.
• PB Imp ("IMP III"): Offered in Standard or Super trim (1968–circa 1970), initially built from UK Mk I kits before transitioning to Mk II kits and engines; some final units may have used CKD Imp Sport shells.
• Hillman GT: Assembled from Sunbeam Imp Sport CKD kits during 1967–1968.
• Hillman Sonic/Stiletto: A convertible model produced by Eiffel Tower Motors in Dandenong for Chrysler Australia.

These models reflected continuous refinements tailored to meet the demands of regional markets.

Variants

• Hillman Imp Mark I (1963–1965)
• Hillman Imp de Luxe Mark I and II (1963–68)
• Hillman Super Imp (1965–1974)
• Hillman Imp (1968–1976)
• Hillman GT (1967–?), developed by Chrysler Australia based on the Singer Chamois Sport; never officially designated as "Hillman Imp GT"
• Hillman Imp Californian (1967–1970), available as coupé and fastback saloon
• Hillman Husky (1967–1970), estate version
• Commer Imp Van (1965–1968)
• Hillman Imp Van (1968–1970)
• Hillman Imp Caledonian (1975–1976), a limited edition (~2,000 units) in Cherry Red with additional accessories, offered in Super and De Luxe trims
• Singer Chamois Mark I and II (1964–1970)
• Singer Chamois Rallye (circa 1965–68), a rally conversion featuring an upgraded instrument cluster, luxury appointments, and a 998cc engine
• Singer Chamois Sport and Coupé (1967–1970)
• Sunbeam Imp Sport (1966–1970)
• Sunbeam Sport (1970–1976)
• Sunbeam Chamois (for export markets outside the UK)
• Sunbeam Stiletto (1967–1972)
• Sunbeam Californian
• Sunbeam Imp Basic and De Luxe Mark I and II (North American market)

Cars using Imp mechanicals

• Beach Mk4
• Bond 875 and variants
• BS Nymph
• Clan Crusader
• Concept Centaur GT
• Davrian
• Ginetta G15 by Ginetta Cars
• Siva Llama

Motorsport

From August 12 to 14, 1964, the Sunbeam Imp sports sedan with registration ZT-86-20 undertook an endurance run across the United States sanctioned by American Rodding Magazine. It shattered a 31-year-old record previously held by Erwin George “Cannonball” Baker since 1933 by covering 3,011 miles between New York City and Los Angeles in 48 hours, 9 minutes, and 54 seconds at an average velocity of 63.7 mph.

The Imp established a notable motorsport legacy, particularly when Rosemary Smith triumphed at the Tulip Rally in 1965. This achievement led Rootes Group to develop a dedicated rally version branded as the Imp Rallye under both Hillman and Singer badges. Although the car faced a contentious disqualification in 1966 after winning the Coupe des Dames category, it retained its strong rallying credentials. In touring car competition, Bill McGovern clinched three successive British Saloon Car Championship titles from 1970 to 1972 driving a Bevan-prepared Sunbeam Imp with minimal factory backing.

Within UK club racing circuits, various versions of the Imp performed exceptionally well in the under-1000 cc Special Saloon class. Prominent drivers included Ian Forrest, Harry Simpson, Ricky Gauld, and Gerry Birrell. Imps remain active participants in historic events such as the HRCR Clubmans Rally Championship.

Internationally, the Imp also enjoyed success in Asian saloon car racing through drivers like Andrew Bryson and Pardaman Singh well into the 1980s. Moreover, the 998 cc engine was adapted for use in three-wheeled racing sidecars throughout the 1970s and 1980s. These modified units often featured custom exhaust systems and Twin Weber carburetors. Such powered outfits competed at the Isle of Man TT races with notable results including Roy Hanks’ eleventh place finish in the 1976 TT 1000cc Sidecar event. Sidecars equipped with Imp engines continue to be competitive within classic racing circles.

In hydroplane racing, Andy Chesman secured the World Hydroplane championship title in 1972 utilizing a highly tuned Imp engine. After acquiring Greetham Engineering, Chesman enhanced this powerplant to deliver 125 bhp at a displacement of 1220 cc fitted with twin Weber carburetors. He established a water speed record of 89 mph at Windermere in October of that year—a record that stood until his passing in 1998.

Additional reading

• Morgan, Tim (May 2017). Hillman Imp: The Essential Buyers Guide. Veloce Publishing.

External links

• The history of the Imp
• The Imp Club website
• Information on the Hillman Imp and its badge-engineered variants
• Andy’s Hillman Imp homepage — comprehensive details on Hillman Imps and their engine derivatives
• How Margaret Thatcher’s policies contributed to the Linwood plant closure — article covering the 50th anniversary of the Imp and the Linwood factory shutdown