Hillman Imp
The Hillman Imp is a small economy car that was made by the Rootes Group and its successor Chrysler Europe from 1963 until 1976. Revealed on 3 May 1963, after much advance publicity, it was the first British mass-produced car with the engine block and cylinder head cast in aluminium.
This unorthodox small/light car was designed for the Rootes Group by Michael Parkes and Tim Fry. It was manufactured at the purpose-built Linwood plant in Scotland. As well as the Hillman marque, there was a series of variations, including an estate car, a van and a coupé.
The Imp enjoyed modest success in both club and international rallying. Rootes introduced a homologation special called the Rally Imp in 1964. It featured many modifications over the standard model, the most important of which was an engine enlarged to 998 cc. Notable successes for this model include the 1965 Tulip Rally in which the works Imps of Rosemary Smith and "Tiny" Lewis finished first and second overall.
Considered ahead of its time, the Imp nevertheless suffered from reliability problems, which harmed its reputation and led to the Rootes Group being taken over by Chrysler Europe in 1967. The Imp continued in production until March 1976, selling just under half a million units in 13 years.
History
Development
Known internally within the Rootes Groups as the APEX project, the Imp came about because of the fuel shortage caused by the Suez Crisis in 1956. Petrol was rationed in the UK, sales of the heavy cars for which Rootes was known had dramatically slumped, and there was a huge market for small economical cars with low fuel usage. The BMC's Mini had already taken advantage of the opportunity, with production starting in 1959. Although the project officially began in 1955, the market for small cars was soon recognised and it was evident that the project would evolve into Rootes' first small, economical car.Seeing an opportunity, Mike Parkes and Tim Fry offered to design the car: "Well, Mike Parkes and I were very good friends. So we went to the director of engineering, B. B. Winter, and said to him we could design you just the car we want. And he said: 'Alright, get on with it then!'". The early stages of development presented "The Slug", which had clear similarities to a bubble car. However, the Rootes design board were not satisfied with this approach, and ordered the design team to press forward. That led to the next stage of the Slug, which appeared more utilitarian with appropriate styling.
Extensive road testing was carried out in Norway in winter conditions, East Africa summer weather and in Arctic conditions in Canada by a small team led by Ken Sharpe
Rootes did previously look at building a small car twice, even if both ultimately contributed little to the development of the Imp. The first being the 1938–1939 Little Jim prototype, which featured a conventional front-engined rear-wheel drive layout equipped with a 750 cc water-cooled engine followed later by the post-war rear-engined 1949 Little Jimmy prototype by Craig Miller that would make use of a Volkswagen-based twin-cylinder engine.
It was originally envisaged by Rootes the 742 cc Coventry Climax FWMA inspired engine would be available in three sizes, 800 cc, 875 cc and 998 cc. However it was not to be as through a combination of engineering production costs, Apex’s increased weight and size, together with experimental dry-liner 998 cc engines being unreliable, resulted in only the 875 cc engine being standardized at the cost of imposing a constraint on the Imp as a one-capacity car that competitors like the Mini did not experience. One alternative solution considered before being dropped was to develop a new taller block giving the engine a longer stroke whilst retaining the 875 cc engine's dry-liners, however this would have been an expensive procedure and would have only been worth the investment had the Imp been a success. A few long-stroke engines were built and evaluated, the work not completely going to waste as they would go on many years later to be bored out up to 1150 cc and used to great in effect in competition by the likes of Paul Emery, Andy Dawson, Ian Carter and others.
The later 998 cc engines in the Rallye Imps meanwhile would on the other hand make use of expensive wet-lines and were not really intended for road use, rather only for competition and further tuning. It was later discovered the largest reliable limit the 875 cc engine would tolerate was 948 cc, however in the absence of more development neither the 948 cc engine nor the envisaged 928 cc engine were used, the latter originally being proposed as early as the mid-1960s for a projected Mark III Imp that became a victim of Chrysler’s cost-cutting before it reappeared years later in the Chrysler Sunbeam.
Mark I Imp: 1963–1965
The Hillman Imp was officially announced on 2 May 1963, when HRH Duke of Edinburgh was invited to open the factory in Linwood. After the opening, he then drove a silver Imp to Glasgow Airport. One of the first Imps produced is currently on display at the Glasgow Museum of Transport. Another early example from 1963 is at the National Motor Museum, Beaulieu, with the registration 1400 SC.Before and after its announcement, the Imp garnered significant attention from the motoring press. In 1962, the Small Car & Mini Owner magazine published an article titled "Enter the AJAX!", particularly noting the all-aluminium water-cooled rear engine. The same year, the Daily Express published an article titled "It's the new 'baby'", calling it "the first baby car ever built by the Rootes Group". In June 1963, the Motor Sport magazine commented on the press' reaction to the Imp who strongly favoured the Imp in terms of its engine, gearbox and competitive price; at launch, the standard model cost £508 1s 3d, while the deluxe version was £532 4s 7d.
The name "Imp" was originally the name of an engine produced by Ailsa Craig Ltd., a manufacturer of marine engines. In 1962 the company was acquired by Warsop Fram Group, and all of Ailsa Craig Ltd's assets were up for sale. The Warsop Fram Group traded the Imp name to the Rootes Group in exchange for a new Humber Super Snipe motor car. The namesake was to emphasize its small-size, and to help it sell as the obvious competitor for the Mini.
The water-cooled four-cylinder power unit was inspired by the Coventry Climax FWMA engine, featuring an all-aluminium alloy overhead camshaft, combined with a full-synchromesh aluminium transaxle. This combination was very advanced at the time. Sir Alec Issigonis, designer of the BMC's Mini, had recently described the fitting of synchromesh on all forward gears as "impossible". Besides the engine's unique design, it was canted at a 45° angle to keep the center of gravity low and optimise road-holding.
As reported in tests such as The Practical Car and Driver, rear-engined cars generally suffer from oversteer handling characteristics to some extent, and to counteract that as much as possible, the Imp has a semi-trailing arm independent rear suspension system. The relatively costly and sophisticated solution, atypical for small-car design at the time, was insisted upon by its designers after lengthy testing of a Chevrolet Corvair with swing axles. To attain balanced handling, the Imp actually used swing axle geometry at the front, but that initially led to too much understeer, and the camber was later reduced by lowering the pivot points.
Gradually increasing in popularity in the UK, Mark I sales in 1963 were estimated at 33,000, and increased to 50,142 in 1964. However, Imp sales decreased in 1965 to 42,663. Reliability problems had quickly surfaced, mainly due to poor cooling of the rear engine, and the public image of the car was becoming negative. That was extremely worrying for the Rootes Group who were trying to compete with the Mini, production of which totalled 1,190,000 during the 1960s.
The Mark I was introduced as a 2-door saloon, which appeared in two models; the Basic and De Luxe. In October 1964, a luxury edition was introduced, known as the Singer Chamois.
Mark II Imp: 1965–1968
Following the initial problems that affected the Mark I, the Rootes Group decided to re-introduce the Imp with significant changes both mechanically and cosmetically.The Mk I Imps had a pneumatic throttle linkage and an automatic choke, both of which were replaced by more conventional items on the Mk II. The Mk II also had improved front suspension geometry, and several trim and detail changes. Although the car was constantly improved over its production life, there was no single change as significant as those in 1965. Among the changes were an added water pump, cylinder head with larger ports and valves, and 'Mark II' emblems on the side of the doors.
Mark III Imp: 1968–1976
The Imp was never officially badged nor referred to as the "Mark III". However, changes were made to the range when the Rootes Group was fully acquired by Chrysler Europe, and so that version is sometimes referred to as the "Chrysler Imp".After Rootes Group's acquisition by Chrysler in 1968, the entire range was revised, except for the Stiletto. The instrument panel and steering wheel were redesigned. The large speedometer previously positioned behind the steering wheel was replaced by a horizontal row of four circular dials/displays of varying detail and complexity, according to the model involved. The right-hand dial, the speedometer, was now to one side of the driver's normal sightline, while one multi-functional stalk on the right side of the steering column replaced the two control stalks that had been directly behind the steering wheel, one on each side. The earlier Imp had been praised for the good ergonomic quality of its dash-board/fascia, and its replacement reflected similar trends in other new and modified UK vehicles at a time of "production rationalization". The more modern arrangement on the Imp was seen by some as a missed opportunity.