Hillman Imp : Rootes Asp

The sporting version of the Imp looks as promising today as it did back during the 1960s. A lack of money would spell its end…

Rootes’ engineers knew that the Imp chassis was capable of handling more power, and decided to work on a sporting variant. Using the existing all alloy ohc engine (tuned somewhat), and allying it to 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 (this was at a time when Chrysler had yet to take a controlling stake in Rootes), allied to negative feedback from America… An ironic decision given the enormous number of MG Midgets and Austin-Healey Sprites BMC managed to shift Stateside.

Pictures supplied by Roy Axe


Pictures supplied by Gerry Ford




  1. Given the negative publicity rear engined American cars were attracting in the states, once Americans gained control of Rootes, any rear engined projects were doomed.

    • Even in Europe it was recognised that FWD was the future, VW was only saved by it’s water cooled front engine expertise brought in from NSU, Renault went front engined with the 4 and Fiat’s last rear engined car was the 127.

      • The 127 was front engined. I think you mean the 126 which was the Polish built successor to the 500

        • The 126 was not a Polish car, it was originally designed and built in Italy. That it was also produced in Poland was part of Fiat’s excellent strategy to expand behind the iron curtain. The last 126 were built in Poland though and – very late in its life – also received a hatchback that was designed in Poland.

      • Even in the mid 60s, it wasn’t as if rear engined cars were instantly old fashioned though. Such a layout would still be common right through the 60s and early 70s

        And in a sports coupe like this, the layout of course lives on in the 911, but also survived for a long time in the French Alpine sports cars.

  2. The yanks were dabbling with FWD then but they started at the wrong end of the market with the Toronado, the exact opposite of economical and practical.

  3. Wonder if this project was the reason why Rootes and Jensen both rejected an approach by TVR to develop the similar Imp-based TVR Tina?

    In the case of the TVR Tina, the proposed production models were to be fabricated out of fibreglass and bonded to the steel Imp subframe, yet not very practical it was believed a metal body would have been too heavy for the engine.

    If only Rootes were in a position to properly develop the Imp engine to make use of Linerless Alloy Blocks (along with taller blocks), allowing for increases in engine capacity beyond 998cc.

    • Given the Clan Crusader’s Lotus background (whether as a replacement for the Seven or replacement/alternative to the Europa), it can be argued Lotus missed a trick in pitching such a car as an entry-level Lotus.

      The Lotus version of the Clan could have certainly benefited from significantly improved exterior styling (since it IMHO fares poorly against the Imp-powered Ginetta G15 and TVR Tina), though not sure which sub 2-litre engines could have slotted above / replace the Imp engines from the mid/late-1970s. The Lotus Slant-4 is certainly out of the question due to treading on the toes of the larger Eclat/Elite and Esprit, as too with the Lotus Twin-Cam from 1975 leaving only the Europa’s Renault A-Type engine (leading to a possible 1.6 turbo version from 1980) or some other alternative.

      Despite being rear-engined the 875-998cc Imp-powered Clan in a number of respects harks back to the original 1216cc Coventry Climax-powered Lotus Elite.

  4. Apparently with the experimental linerless 998cc engine, the Asp prototype had a top speed of around 105-106 mph.

    That is compared to the MG Midget 1275/1500 or the 1300/1500-engined Triumph Spitfire, which had a top speed of around 95-101 mph and 100-101 mph respectively.

  5. ‘the last fiat with a rear engine was the 126’
    Everybody forgets the italian masterpiece that wasnt the fiat X1/9 !
    It wasnt that bad, apart from rust. A friend had one and rain filled the doors with water, every corner the tide came in.

  6. Had the Asp been built, it would have been fascinating seeing it powered by the unbuilt 1148cc tall-block Imp unit (and carried over to the Imp as a Mini 1275GT/Cooper S rival) or even the 1250-1750cc+ Swallow engines (in the event a larger Swallow-based Asp model as a Sunbeam Alpine successor is not considered).

    As for the Fiat X1/9, it could have done with both the 1.3-1.4 Turbo used in the Uno/Punto (which was apparently considered at one point) as well as the 1.6 Fiat 128 engines.

  7. Been reading a bit online about a late Imp engine specialist called Ian Carter who was apparently involved with Rootes Motorsport division as well as with the Asp, etc.

    It seems that in addition to utilizing the experimental 1150cc tall-block Imp engines for motorsport, he also over the years managed to achieve increasing the displacement of the Imp units even further to 1197-1204cc up to as much as 1237-1268cc.

    While it is questionable whether a productionized version of the tall-block 998-1150cc Imp engine in better circumstances would have been able to reach such heights in engine capacity for road-going models, it is assuming to think the Imp would have been able to more than match the Mini 1275 Cooper S (as was the case with the Imp vs the Mini 970 Cooper S or standard Imp vs Mini 998).

  8. EWM
    The ASP was powered by a 998cc Cross engine giving 61.5 bhp. This was an arrangement being developed by the Cross company in Bath where the pistons with a wide cast iron rings ran directly in the aluminium. At the time, Engineering were interested in investigating this arrangement. I still have a copy of the performance tests carried out at MIRA on the evening of the 30.9 1964 by Morris Evans and Jimmy Kilbride. It achieved a 0 to 60 in 12.76 secs. and a maximum of 103.5 with the headlamps recessed and 97.6 with them raised.
    The largest capacity engine we built in the Competitions department for Colin Malkin to rally in the Imp was 1133cc. This was a combination of the intended 998cc long stroke production engine ( which never saw the light of day) and the increased bore 998 with the 875 stroke used in the rally Imps.
    Ah, what might have been!

    • Thanks for the information and background.

      It is interesting to compare the output of the engine used in the Asp to the Rallye Imp, though assume there was scope for a bit more power on the tuning front had the engine reached full production.

      Was 1133cc the actual displacement of the 1150cc experimental tall-block engine mentioned in both the Henshaw and Mowat-Brown books or a separate development? Since have read the displacement of the 1150cc was reputedly carried over to tuned versions of the Imp like the Emery GTI as an option via a 75mm bore / 65mm stroke (though Alan Fraser was able to increase the displacement to 1142cc with others like Ian Carter managing to achieve larger displacements via 67-70mm+ stroke, etc).

  9. Wynne Mitchell

    I can only quote what occurred within the factory. I know a lot went on outside with different tuning and engine development companies.
    The production intention was that the Imp engine size was to start as 800cc., to increase to 875, then 1,000cc..I think one or two of the early prototypes were fitted with 800cc. engines but they were considered underpowered as the car was heavier than originally anticipated. They were unable to complete the restart test on the M.I.R.A. 1 in 3 gradient, fully laden, which was a Rootes requirement.
    Therefore the engine went into production at 875cc.
    The intention was that in time, the engine would be enlarged to 998cc. by increasing the stroke. This required a taller block by about 0.6 in. and the production block machining equipment at Linwood was designed to accommodate this. The stroke was increased from approx. 60.4 mm. to 68.72. The 1133cc. engine we built used a prototype sandcast tall block supplied by the Engineering department, one of a number they had in stock. Again, approx. 72.5 mm. bore by 68.72 stroke. We did not carry out any further Imp work after 1972 as the Avenger occupied all our time.

    I have come across some engine power curves dating back to 1972 outlining the power and torque outputs of various engine configurations we had. If I remember correctly, all these tests were carried out on the Engineering test beds at Ryton, the engines being to rally specification i.e aircleaner etc.
    A summary is as follows:-
    Imp Sport, 875cc., 51.5 bhp,, 49.5 lb.ft. torque.
    998 Sport. This was possibly the Rallye spec.,54.5 bhp and 57 lb.ft.
    The 998 works rally spec with a .31 camshaft, 64 bhp, 62 lb.ft.
    The above engine with a .36 camshaft, 70 bhp.,64 lb.ft. Both these were fitted with what was known as a Group 3 cylinder head.
    The 998cc. rally engine with Weber carbs etc. gave 92 bhp. and 71.5 lb.ft.

    We also carried out some test work on the test bed at Engine Development, Rugby, comparing the camshafts which were available to us at the time, R17 to R23. Here the power outputs varied from 93.5 to 98 bhp. 998cc., Weber carbs.

    The Asp which was performance tested must have had a good head prepared by Engineering. The problem with the Cross configuration was that it was very difficult to run in, suffering from bore `pick up` which rendered it unsuitable for a mass production application.

  10. One area about the Asp that is not completely clear would be whether it was still to be rear-engined notwithstanding the front-mounted radiator or actually feature a transverse front-engined rear-wheel-drive layout, some say is it is the former while others (Imps4ever, Jensen V8 by Mark Dollery, etc) state the latter is accurate.

    • To be clear Imps4ever has the Asp prototype as a front-engined sportscar though nothing about the engine being transverse.

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