The engine was totally unlike the mini's. The mini used a very traditional cast iron block,
mounted transversely at the front, whereas the Imp, breaking new ground, took a light alloy overhead cam engine derived from the famous Coventry Climax engine used in Grand Prix racing cars, and mounted at the rear, driving through an all-new transaxle. My little car was the same year as this, and I really loved it. Yes, it was a flimsy tinny box, but incredibly light and manoeuvrable. That was also its downfall. I don't suppose it ever was wind-tunnel tested in design, as, at speeds over about sixty, the front end tended to lift and with the weight off the front wheels, it would wander a bit. Big trucks displace a lot of air, and the Imp would get blown sideways. A company marketed a solution, they called it a 'Hermes Aerofoil', a wing that bolted on under the front end to provide an aerodynamic downforce. I had a different solution. Ten or fifteen gallons of water, kept in collapsible camping-type bags in the front. That kept it in line, and could be emptied and squished flat if the space was needed.
The car had several other design flaws. The cold start mechanism was an auto choke. It never worked very well. Thus, frosty mornings could be a nightmare I used to pour a kettleful of boiling water over the inlet manifold, which usually worked. Also, the cooling system was all at the back, and was barely able to cope on a good day. If it was a warm day, traffic was stop-start, you could pretty much guarantee overheating, and serious overheating meant the head gasket would fail. I became adept at stripping and reassembling the top end of the engine.
Still, the car was a friend, replaced with a new, improved version that we had for less than a year when some old fool failed to notice the red light and stopped traffic ahead, and drove into the back of it.
I also had a Mini, around those years. The imp was more comfortable, had better space inside, but the mini...
The mini was like a mad little roller-skate on steroids. You could throw it into corners on country roads and fly around them, you could drive flat-out and be totally in control. If I was trying to be a respectable gentleman of suburbia, I'd choose the Imp any day.
But if I wanted to be an uncontrollable hooligan laughing crazily as I drove... Um. Well. I was younger then... It had to be the Mini.