Welcome To The Hillman Owners Club Of Australia Inc Imps Page

Rootes' small car was designed by Michael Parkes (a development engineer for Ferrari) and Tim Fry more or less from 1955 on. It was made in the purpose build Linwood factories in Scotland. Launched in 1963, it sported many new and untried ideas, like an aluminium alloy engine, and overhead camshaft; a pneumatic throttle and king-pins running in sealed plastic bearings. It was produced for more than 12 years, until 1976.

In 1955 a small car project was begun, not so much to come up with an economy car in the Suez Crisis days (like the Mini), but to provide an idea of what sort of affordable car could be made and what its performance would be. Parkes and Fry proposed a 2 adults - 2 children car, that could do 60 mph and manage 60 mpg (which made aerodynamics a priority). Looking at the competition (Fiat 500, BMW 700, Citroen 2CV) and considering costs, they opted for a rear engine. Other aims of the team included that the small car be fun to drive.
Creative automotive design flourished in the late 1950s and early 1960s, especially in the U.K. Most auto enthusiasts are aware of the transverse-engine front wheel drive Austin Mini, designed by Alec Issigonis. The Mini's basic power train layout, so brilliant because of its compact packaging, continues to serve as the blueprint for almost every passenger car line in production today. However, the Mini was not the only small British sedan worthy of our interest. The U.K. also produced its own "Poor Man's Porsche".

At the same time that Chevrolet was developing prototypes for the Corvair, the Rootes Group in England was designing a smaller but similar rear engine economy car, the Hillman Imp. Development of the Imp began in 1955, but production did not start until 1963, three years after the Corvair was introduced. The Imp remained in the Rootes line up until 1976.

Head-on, the Imp looks like a miniature early series Corvair. The resemblance is more than coincidental. While Rootes stylists were borrowing contours from the Corvair body, Rootes engineers were test-driving Corvairs, looking for technical solutions to rear engine design problems. Unlike their counterparts in the styling department, the engineers didn't copy the Corvair so readily. After crashing one 'Vair rather severely at the test track, Rootes rejected swing axles and adopted a fully articulated multi-link rear suspension for the Imp. And, to minimize rearward weight bias, the Rootes engineering staff insisted on a lightweight all-aluminium engine.

And what an engine it was! For the basic layout, Rootes engineers called upon Coventry Climax, one of the most renowned engine designers in the world. Coventry Climax engines powered some of that period's most successful Formula 1 cars, including the Lotus 18 and the Cooper T51. Coventry Climax was eager to capitalize on its racing success and sold Rootes the production rights to a state of the art overhead cam 750 cc four cylinder engine. Rootes proceeded to modify the design to make it suitable for the Imp by opening it up to 875 cc, laying it over on a 45 degree angle, increasing the compression ratio to 10:1, and die-casting the block and head in aluminium.

One of the problems of an aluminium block is that, without steel liners, cylinder bores are subject to premature wear. However, the process of pressing steel cylinder liners into an aluminium block represents a considerable manufacturing expense. Like the engineers who developed the Corvair engine, Rootes almost specified a hard high-silicon alloy to negate the need for liners. However, again like their counterparts at GM, Rootes found that it could not master the technique of machining this unproven material.

Rather than give up, Rootes chose another alternative, opting for an aluminium block with iron liners cast in-situ, just like Buick's 1961 aluminium V-8. The quest for weight reduction paid off. The finished engine weighed just 170 pounds, "including accessories."

The little Climax engine was water-cooled, so the engineers positioned the radiator alongside the engine behind the rear seat. This solution, common to the Fiat 600, Simca 1000, Renault R8, and a number of other European rear engine cars, compromised cooling efficiency but avoided the need to mount the radiator in the front luggage compartment. This simplified the plumbing and provided a modest boost in luggage space.

Like most innovative cars, Imps gained a reputation for teething problems. Rootes worked hard to correct these problems, but most consumers in the English economy car market took the conservative approach and selected Brand X instead. Over thirteen years of production, about 500,000 Imps were sold. 

Sports car enthusiasts, however, recognized that the Imp offered great driving fun at reasonable cost. The Coventry Climax engine was smooth and could be revved with confidence up to 7,000 rpm. English car magazines raved about the Imp's excellent handling, which apparently was as good as the Austin Mini's. All over the Isles, enthusiasts entered Imps in club events for many years. Two specialty manufacturers, Ginetta and Clan, produced hand-built sports cars based on Imp components, quite similar to the Corvair-based Fitch Phoenix in concept.

The Hillman Owners Club Of Australia Inc wishes to extend to all Imp owners, who are members of the HOCA Inc, a warm and hearty welcome to all H.O.C.A. events and general meetings. So come along and meet some of the other members of your club, you may just enjoy yourself.