Olly and Matt Clark with the Gobstopper II
There are three immaculate Subaru Impreza Turbos in the equally immaculate workshop of Roger Clark Motorsport (RCM).
The first belongs to an Icelandic drag racer; the other two are RCM’s famous Gobstopper I and Gobstopper II hillclimb and sprint cars.
Driving Gobstopper II, Olly Clark set the overall fastest time up the hill at the Goodwood Festival of Speed both last year and this year. But those successes weren’t just about Olly’s wheelmanship; they were also down to the engineering skills of his brother, Matt.
“Matt is the engineering mastermind who comes up with the technical ideas while I figure out how to pay for them,” says Olly. Their business is 95% mail order parts supply and 5% hands-on preparation and tuning of Imprezas.
RCM has prepared and rallied Imprezas since Prodrive introduced them to the World Rally Championship in the 1990s. Then in 2006 a drag racing customer asked the brothers, sons of the late British rally legend Roger Clark, to build an Impreza capable of running a nine-second quarter mile.
“We took WRC technology and ran a bigger turbo,” says Olly. In those days Imprezas weren’t making much more than 400bhp; a lot more would be needed to break 10 seconds.
The Clarks began to commission the special parts needed to cope with very high power, and the customer ended up with 850bhp and ran nine seconds with a terminal speed of 148mph. The project led to the development of a high-performance demo car for RCM that would evolve into Gobstopper I.
Gobstopper was so named because the Clarks wanted to silence critical keyboard warriors. In 2004 they entered Ten of the Best (TOTB) at Elvington, an event consisting of a quarter-mile dash, top speed over one mile and a handling circuit. Olly then drove in Time Attack at Donington in 2007 and came second after getting advice from family friend and BTCC ace Matt Neal. In its final form, Gobstopper ran a 9.2sec quarter and hit 194mph in 1km from a standing start. “It was like being strapped to a missile,” recalls Olly.
By then the 2.0-litre flat four engine was developing 880bhp and 680lb ft using nitrous oxide and race fuel. In total, Gobstopper I won TOTB three years running and two Time Attack Pro titles in a row.
Gobstopper II followed in 2014, based on a Japanese-market Version 6 STi. The body is a work of art involving around 1000 hours of fabrication and welds that look like surgical sutures, and it includes custom carbonfibre front wings and a huge rear wing. At 160mph the downforce is 200kg at the front and 500kg at the rear. The aerodynamics were developed from a 3D scan of the car and by using computational fluid dynamics.
Gobstopper II runs an advanced nine-setting ABS set-up, operated via a digital instrument display. “You always have steering, even when it’s really wet,” says Olly. “But when it’s drier and the car might be lifting wheels you need a less sensitive setting. With a full slick you can let the tyre do its thing.” Gobstopper II uses 366mm cast iron AP Racing discs for short tracks where there’s less opportunity to warm them, and carbon brakes with 380mm front and 340mm rear discs for longer tracks. The dash displays a real-time readout of the front-rear brake balance, so Olly can always see exactly what’s going on.
Despite the car’s spec, Olly says Gobstopper II is much easier to drive than Gobstopper I, but some of his father’s talent has obviously rubbed off. The team won the Time Attack Pro Championship again in 2014 and on that basis was invited to the following year’s Festival of Speed, where they beat all comers.
It’s not hard to see how they did it. The technology, build quality, equipment levels and preparation of Gobstopper II are closer to that of an F1 car than any saloon. Now, with development complete and the setup perfected, it will be fascinating to see what next year brings.