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Hillman Imp

This is my experience of owning a Hillman Imp.

I purchased a brand new Hillman Imp in 1969 which was then owned by Chrysler with some Australian content. It was used as a first car, retired to a second car, and then in 1979 put into storage for many years. In 2012 the Imp came out of storage and is being restored for a club permit.

Like all British cars, the quality and reliability were affected by poor industrial relations. Quote from Top Gear on the demise of the British motor industry: “The workers spent more time picking at the gates than building cars”. Rootes Group (Hillman and Humber cars) suffered from industrial action and they never recovered and sold off or taken over by Chrysler. My next car was a Japanese/Australian car (Datsun 1200) assembled in Port Melbourne with Japanese and some Australian parts. The Japanese industrial relations were different and workers were looked after resulting in reliability and quality being so much better.

I am not union bashing, I have been a union member. There needs to be a balance of power between unions and management. If either side has too much control then the outcomes are not good.

What they go right

Good fuel economy and uses Super petrol like most cars of the time. I could not use Standard petrol due to the high compression ratio of 10:1. It needed 95/97 octane fuel. I got 36 to 44mpg ( 7.8 to 6.5L/100km). Being a small car it used every space like the Mini.

No rust. It had no mud traps on under-body so there was no structural rust. The car spent a lot of time on dirt roads as our parents live 10km from the sealed road. My car has only condense rust on one spot of the bonnet.

The engine was reasonably easy to work on, but it required a different technique. Kneel on foam at the back of the engine, and say to it, be a good little Imp.

The exhaust system was the most reliable part of the car. I consisted only of a muffler that lasted the life of the car.

What they got wrong

The car had an Aluminium engine with a cast-in steel liner for the bore. The water required a rust inhibitor. The small bolts on the engine required only 6ft.lb torque which is only finger tight. This may have caused problems, I used a torque wrench for all engine bolts. These issues may have caused problems at the time.

The car suffered from poor reliability, being the last made they used up all the rejected parts. I had to replace the exhaust valve in the number 3 cylinder 3 times and only fixed the problem when I fitted another head from a car I purchased for spare parts. I think the head casting had a defect in the water jacket.

The gear lever entered the gearbox at the bottom and the oil seal leaked out of the seal, a design fault.

The 4-wheel independent suspension did not keep wheels perpendicular to the road. This caused the inside tire to wear, tyre rotation did not help. Tyre life was only fair, not good for economy cars.

The engine had to be short to fit under the rear boot, the engine was on a slant but it also had short connecting rods. The short connecting rod made too big an angle with the bore, which put too much side thrust on the bore, causing a short engine life. Vectors will show this ( see below). For a given force 'F' the force onto the bore 'A' is much greater. I put a rebuilt engine in at 40,000 miles (64,000km). A better design would be a water-cooled beetle engine. The car was not driven hard, it was driven for the economy as I did not have much money back in those days with a young family. My next car was a Datsun 1200 and its motor did 150,000 miles (240,000km) without the head being taken off.

To keep service costs low they did not have grease nipples. The kingpins were hard-chrome plated with Teflon-coated steel bushes. The steel corroded under the chrome failing. When replaced I fitted grease nipples, greasing pushes out the water and dirt.

When I purchased the Hillman Imp a Renault R10 was also on the shortlist, it would have been a much more reliable car. My experience with the Imp taught me to become a motor mechanic and I have a historical car to restore.





Vector diagram showing high side force on the bore. With shorter connecting rods the angle it makes to the bore the greater. This results in greater force on the side walls (A). Therefore greater wear on the bore, rings, and pistons.
This article was first published in the Backfire: September 2018 (WDHVC) Revised 1/12/24

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