Aston Martin specialist Richard Williams, who managed the firm’s Group C racing activities from 1984-1989, has developed a lusty seven-litre conversion for the race-bred V8 engine.
Even before the Newport Pagnell company announced the Virage Vantage with its 550 bhp twin-supercharged engine, Williams based in Cobham, Surrey had already eclipsed the factory by putting his seven-litre, two-valve engine on the market with 510 horsepower, or 480bhp for automatic transmission models.
The Williams SEV8N, as he calls the conversion, is not cheap. The cost is £25,000 before tax and VAT are added, and includes modifications to the engine, gearbox and differential mountings, redesigned torque converter, oil cooler and a special alloy sump.
“It makes a lot of sense if your engine has done a high mileage and needs a rebuild,” says Williams. To make his point, he made available a customer’s Aston Martin V8 saloon first registered in 1974.
Despite the automatic transmission, the heavy brakes and floating suspension characteristics, the old car responded well to the tuning treatment. The seven-litre engine bellows through the huge silencer system, attracting a good deal of attention, but the car lunges towards 120 mph like a hunting dog on a leash.
The full value of the conversion became apparent in a Zagato Coupe, no lightweight at I 650 kg but far lighter than the V8 saloons. The fully-tuned seven-litre engine endows the Aston with astonishing performance, possibly on a par with the Ferrari F40.
The Aston Zagato reached 130 mph in an unbelievably short space of time on a dual carriageway… in fifth gear, accelerating like most cars do in first and second!
The Williams version retains the two-valve-per-cylinder layout, but adds a ‘beak’ in the combustion chamber to induce squish. The inlet ports are offset to improve efficiency and flat-top pistons replace the standard domed pistons.
Williams doesn’t reveal the exact bore and stroke (“there are too many people copying us in this business”) but says that the V8 has reached its limit at seven litres. The two-valve, 5.3-litre V8 was producing 305 bhp when it went out of production, so the conversion increases the output by well over 50 per cent.
No matter how old the engine may be, it can be restored with new liners, pistons, rods and crankshaft. As the cylinder heads are rebuilt they are adapted for lead-free fuel, and a catalytic converter is on the options list. This, Williams says, “reduces the exhaust noise to quite acceptable levels”.