This stunning Sapphire Cosworth is unlike any other, thanks to a homebuilt 764bhp YB engine and a sequential gearbox that help it cover the quarter mile in just 10.3 seconds…

Feature from Fast Ford. Words: Simon Holmes. Photos: Matt Woods

Over the years, it’s fair to say we’ve seen plenty of well modified Cosworths pass through Fast Ford pages. Both heavily fettled track cars with race specifications, or full road cars hiding huge power have become fairly regular, which is no bad thing. But of all the massively modified YB powered Fords we’ve featured, we don’t think we’ve ever come across something quite like Jon Gamble’s Sierra Sapphire Cosworth 4×4.

For a start, it’s putting out a serious 764bhp, thanks to hefty sized, twin-scroll BorgWarner turbo producing 2.5bar of boost. It then sends all that horsepower through a trick six-speed sequential gearbox and down to the Tarmac via a set of stunning centre-lock wheels that look they’ve come straight off a RS500 touring car. That little lot alone is enough to firmly place this Sapphire Cosworth ahead of virtually any other of its kind, but then there’s the fact it also happens to be a true road car, with a full interior and tyres to prove it. Yet this tidy Sapphire covers the quarter mile in a blistering 10.3 seconds and, perhaps most impressively of all, was largely built by Jon at home in the garage.

Sapphire Cosworth

Only a handful of fast Fords, let alone Sierras of this type have ever been able to boast those sort of credentials, as it takes a serious amount of time, money and effort to create what is quite simply one of the best Sierra Sapphires we’ve seen.

The journey to bring the car to this level wasn’t short or easy either, as Jon explains to us that he has owned the car for some 14 years. He originally bought it as a toy, for use as a hobby in his spare time, back when the Cosworth was the best choice for modifying, long before the Focus ST and RS models became so popular.

Jon sourced the car from Ebay and when he first got hold of it, it was completely standard.

“Apart from a set of alloys and 360bhp chip,” he recalls. “I didn’t really have any real plans for it back then exactly, it just grew as I went along.”

The first modifications on the Sapphire Cosworth came in the shape of a Spec-R intercooler and a twin-scroll BorgWarner turbo set up from Nortech Performance, both of which are companies Jon has formed trust in over the years thanks to their good reputations. For most other things, Jon works on the car himself where possible, which explains how and why the Sierra began to develop quickly into a very serious machine. This evolution was further helped by his interest in drag racing, which developed around 8 years ago.

“It began with ‘Run What You Brung’ events with my sons and has become more serious since then,” he reveals. “My aim became to make it the fastest Sierra on the quarter mile, but I still wanted to keep it street legal and useable.”

Sapphire Cosworth

Sure enough, Jon used to drive the car to Santa Pod, before racing it and then bravely driving home again, but as the power and performance rose, the odd breakage did occur. In fact, it was when the build reached a very respectable 521bhp and the gearbox blew that Jon admitted that he should start trailering the car to events if it was going to be driven hard. It was also at that point Jon became more serious in bettering his times, and the build promptly grew from there.

In 2019, Jon took a huge step up when he built the new engine in his garage at home, which featured some serious components, such as a steel crank, linered block and a tasty ported head, which helped it produce a colossal 707bhp on pump fuel and 764bhp, together with 604lb.ft of torque, on more potent 110RON race fuel.

Sapphire Cosworth

To go with all that the new found power was the heavily uprated transmission Jon had selected to replace his last broken gearbox. It was not only better suited to the job but also improved the car’s performance on the strip, thanks to lightning fast gear changes.

“I went to a sequential gearbox when Oppliger Motorsport brought out a new six-speed that fitted in the old MT75 casing,” recalls Jon. “It also meant I could flat shift when racing and the gearbox made the single most amount of difference to the way the car drove.”

As four-wheel drive Cosworths are prone to weak drivetrains, both the front and rear differentials have also been beefed up to suit using Quaife items and so far proven reliable despite the numerous hard launches at Santa Pod.

Sapphire Cosworth

At this point, despite the huge performance, the car had always retained a standard look, with the bodywork complimented only by a set of understated Compomotive wheels finished in black. But that look changed more recently when Jon opted to mix things up a bit and fit those awesome centre-lock split rims. It was an inspired choice.

“I don’t know of, or have ever seen, any RS500 touring car replica wheels on a Sapphire Cosworth, so thought why not!” he tells. “The wheels are made up by MT Motorsport, who made the centres and uses genuine BBS inner and outer rims. They’re wrapped in 215/45/17 Toyo R888R tyres all round.”

Although they’re wheels usually associated with track day cars, the polished lips and gold centres suit the car well and those in the know realise they’re a serious bit of kit, which is perfectly in keeping with the car’s look.

But whilst there are subtle hints on the outside, the interior remains virtually completely standard with a full trim both front and back. However, There are a couple of tell-tales for eager-eyed Ford fans, such as the gauges, harnesses and that extended gear lever that hints there’s a special gearbox hiding beneath it.

Despite the huge power on tap and tasty transmission, Jon does still use the car on the road when he finds the time and isn’t at Santa Pod. Although the ballistic performance of a true 10-second street car does require a lot of respect and self control.

“I still take the car out to meets at Ace Cafe and to shows when I can, and had it on track at Ford Fair too. It’s a right handful!” he confirms. “I like the whole driving experience. It’s like riding a very fast motorbike in terms of speed and stopping distances.”

With a best time of 10.3 seconds at 141mph on road tyres so far, there’s certainly a lot more to be had from this Sierra just by swapping over to a set of drag radials, but Jon isn’t in a rush to make that move just yet, keen to keep it street legal. There are plans to improve the car further, with talk of a side exit exhaust system, lightweight body panels and an increase in power in order to see the quarter mile time fall. We’re guessing this will be one of those projects that continues to evolve, and we’re certainly looking forward to where it goes next.

Sapphire Cosworth

Tech Spec: Modified Sierra Sapphire Cosworth 4×4


YB 200 Ductile linered block, CP forged pistons, steel rods, Arrow steel crankshaft, ported head, uprated cams, adjustable pulleys, big wing sump, BorgWarner 91/80 EFR twin-scroll turbo, twin TiAL external wastegates, Nortech Performance twin-scroll tubular exhaust manifold and 3.5in exhaust system, Spec-R intercooler, rad and WRC style breather set up, Roose Motorsport silicone hoses, custom intake with K&N filter, Autronic SM4 ECU


Oppliger Motorsport six-speed sequential gearbox, Quaife front and rear diffs with 3.6:1 ratios, TTV twin-plate 230mm three-piece clutch kit


GAZ Gold coilovers, front compression struts, custom front strut brace, poly bushed


AP Racing four-pot calipers and 330mm discs at the front, standard calipers and 300mm discs at the rear

Wheels & Tyres:

BBS inner and outer split rims with MT Motorsport centres, 215/45/17 Toyo R888R tyres all round, MT Motorsport centre-lock hub adapters


Original Smokestone Blue paint, RS500 style front splitter, quick release front bumper on Aerocatches modified for airflow


Original dark cloth trim, Willians four-point harnesses, Stack gauges, digital gear indicator