The C4 ZR-1 was a bulletproof beast | Thank Frankel it’s Friday | GRR

I was given an E34 BMW 530i for the trip down and a photographer who refused to drive so much as a yard on the unassailable logic that he was a photographer who took the photographs, so as I was a driver, I should do the driving… We did in a day a distance I had never driven before, drove the Vette the following day and then drove home by which time I’d got a little braver. At a fuel stop while he went for a comfort break I got into the passenger seat and refused to budge.

But back to the ZR-1. This was based on the C4 generation of Corvette and was of considerable interest because not only was it suggested it might be the fastest production car in the world, but also because much of the work that had been done to make it that way had been carried out by Lotus, which was at the time newly acquired by General Motors.

The most significant modification was to take the famous old small block motor and turn it into something previously unimagined. Out went the pushrod operated valves, replaced by new cylinder heads atop an aluminium block comprising twin overhead camshafts per bank and four valves per cylinder. Or two. The car came with a lockable switch that allowed you to choose whether the engine would run on all 32 valves, or in the event it was being valet parked or driven by your children, just 16 which had a seriously limiting effect on performance.

What do I remember of it? A car with huge performance, right across the rev-range. I had by then driven a Ferrari Testarossa and the big Vette seemed at least as fast to me. And it sounded terrific. But I remember even more its handling balance and the way it would settle into endless drifts at quite high speeds as if born to it. To a cub road tester who still had it in his brain that all American cars couldn’t go around corners, it was quite an education. And a simply terrible interior. I remember that too.

But most of all I remember trying to extract the performance figures because it wasn’t a happy experience. Back then I considered myself something of a dab hand at the curious art of making a car accelerate as fast as possible. And the ZR-1 wasn’t difficult. Some cars have high first gears, sharp clutches, unpredictable throttle response, spiky torque curves or simply too much traction, any one or combination of which could make the job of getting the optimum 0-60mph time something of a headache. The ZR-1 had no such problems. Time and again it would light up its rear Goodyear Gatorbacks to just the right amount, thrust the car forward, soon accept full throttle after which I just had to change gear as late and fast as possible and the job was done.

Except it wasn’t. I can’t remember the exact numbers now and they don’t really matter. What I do remember is not being able to get within two or three-tenths of Chevrolet’s claim for the car, and we’d brought our heavy but accurate Datron timing equipment in the boot of the BMW, so there was no doubting the data. I tried again and again, the photographer sitting next to me as ballast, for once not enjoying his role as passenger quite so much. But still, the numbers didn’t come. I must have done 20 standing starts, probably five times as many as I’d do in normal circumstances, but it just wasn’t working. But at least the car was strong: anything else would likely have blown its clutch, gearbox or other driveline components by then.

So I concluded that Chevrolet was being a touch economical with the truth and, to test my theory, I invited the chief test driver to try and replicate his claimed numbers. It was only then I discovered they did their tests with only the driver on board, saving the 75kg of passenger or ballast we always carried. But that couldn’t account for it all.

But he duly smoked off in the car and when he came back, the numbers spewing out of the machine needed no interpretation: they were exactly what the company had claimed. I couldn’t believe my eyes, so much so I insisted he did it again, but with me on board. ‘Sure,’ he replied.

He squealed off the line just as I had, but when that gearchange came I couldn’t believe what he did next. Or didn’t do. He didn’t lift. Leaving his right foot nailed to the bulkhead and dipping the clutch only long enough to make it disengage first, he wrenched the gear lever back, forcing it into second while the engine repeatedly headbutted the limiter. I’d always wondered what powershifting was, and now I knew.

And I also knew that when I had thought that car was strong, I hadn’t known the half of it. How that transmission put up with the treatment I’ll never know. But that’s how they got their numbers. But it did leave me with a dilemma. Did we print our figures in the knowledge they did not reflect the car’s ultimate capability, or did I re-run the test Chevy-style and get a set of numbers that would look fabulous on the page, not least because they’d probably show the car outperforming Ferrari’s flagship. What do you think? We ran with the slower numbers because to do anything else would be to confer an unfair advantage on the car not enjoyed by any other we’d tested, all of which were evaluated within strict testing protocols including having two people on board. And taking your foot off the bloody throttle while changing gear…