By the standards of the time, the aluminium 3.5-litre V8 in the front of the Rover SD1 was quiet, smooth, fast and flexible.
So did the five-seat hatchback really need extra oompf? Tuning specialist Janspeed certainly thought so: for a cost of £960 (excluding fitting) the Salisbury-based company would add two turbochargers, providing 30% increases in power and torque, even more flexibility and a BMW and Jaguar-worrying 140mph top speed.
The Rover 3500 V8 SD1 Janspeed Turbo conversion’s party piece was described by Autocar road tester John Miles in a 1979 test: “Bring the speed of the Janspeed Rover down in fifth gear to under 10mph (350rpm). Then floor the throttle. A little above 10mph the slight shudder gives way to a totally smooth and ever-gathering pull from there to around twice the legal speed limit. A V12 Jaguar owner might not be impressed but the rest will be.”
According to Janspeed proprietor Jan Odor, the conversion didn’t require any modifications to the engine itself. The standard carburettors, air cleaner and air inlet temperature control valve were all retained, with a pair of US-derived Rotomaster Turbosonic units, one to each bank of cylinders, bolted on.
The standard car had an official 0-60mph time of 8.4sec; Autocar’s test equipment measured 8.2sec on the Rover 3500 V8 SD1 Janspeed Turbo.
Although that wasn’t the most dramatic of improvements, it was only part of the story. “It has an incredibly smooth transition on to boost at 1700rpm on full throttle, and unboosted part-throttle performance virtually equal to the standard car,” described Miles. “Use full throttle, keep the engine above 3000rpm and it cuts the standard car’s acceleration times to ribbons.”
When it came to taking the figures at the test track, teeming rain limited the speeds attainable in safety to just over 110mph. Using a suggested rev limit of 5500rpm, Miles calculated that a top speed of 146mph was possible.
Although the engine modifications drew praise, other modifications to the SD1 were less well received.
“Odor had decided, in the interests of on-limit handling predictability, to change the SD1’s hydraulic strut/coil spring self-levelling rear suspension to the straight coil springs from the Rover 2300,” wrote Miles.
“Whether a Rover Turbo owner will want to charge through corners to take advantage of such a set-up is another matter. Likewise, stiff Koni front and Schreider rear dampers felt misplaced.
“But perhaps most incompatible of all to steering and chassis character were the 205/60VR-14 Dunlop Sport Super tyres mounted on 7in wide alloy rims.
“The terrible weather suggested that they might provide some extra traction. They probably did, but together with the suspension settings their stiff sidewalls made the car nervous and over-responsive to the steering and board-like to ride in over poor surfaces.