Theon Design Porsche 911 review

On the day we arrive to try CHI001 – a 400bhp 964 conversion destined for Chile and equipped with the lairiest engine yet conceived by Theon – there are three cars at differing stages of construction inside the discreet workshop. All have been stripped back to the bare metal, straightened, strengthened and cloaked in hand-beaten steel or, in the case of CHI001, beautifully wrought carbonfibre (though the doors are steel, for crash-protection).

All bear flat-six engines based on the 3.6-litre block they were born with, though the outputs are way in excess of the 247bhp the basic Carrera had back in 1990 and comfortably more than even the 316bhp of the whale-tail Turbo. Go to Theon and your options currently range from around 370bhp up to 450bhp in the case of the middle car of the three, whose Rotrex-supercharged heart nestles beautifully inside its neat, quad-piped tail. One for another time, I hope.

Previously, Theon's engines were built in Brackley by Nick Fulljames, formerly of Autofarm and a man whose experience extends from working with Cosworth in Formula 1 to Jaguar, alongside TWR. However, this latest unit for CHI001 has been made built in-house. At four litres and naturally aspirated it's also the is the largest Theon offers. The brief from the client was something I suspect we'd all desire: usability with some bare-chested, RSR-y headiness. It’s why this car uses a single-mass flywheel and quite fighty cams. There are also individual throttle bodies, which sit underneath stacks (in this case not polished, but crackle-coated) that artfully curve inwards and over the carbonfibre engine shroud. Directly beneath it all sits the G50 transmission from a 993-generation 911, stripped and rebuilt and now equipped with an LSD from Wavetrac.

As for the exterior, you could take in the details for an inordinate amount of the time. The 17in dished wheels are Champagne-hued works of art, the brightwork so nicely done, the carbon body truly glove-like in its fit. It’s all very pretty. 

But now it’s time to slide aboard the mechanical blueberry and into the grip of a modern Recaro bucket. Seat aside, this cabin feels of its time – flamboyant as you want and with lots of inventive textures, but of its time and true to the original 964, which I suppose is the idea, though this doesn't come without compromises. The drilled pedals look fantastic but are typically offset. The Nardi wheel feels so reassuringly simple and firm but is two inches closer to the upright windscreen than you’d want.

Visibility is phenomenally good by modern standards, though, and the dials equally clear. It’s an exciting and tactile place to sit but this is nothing compared to what happens when you fire the engine. At this point the entire chassis begins to pulsate to a syncopated beat, as though some creature is attempting to break its way out. Hawley insists that all Theon’s cars are docile enough for daily driving but CHI001’s hollow air-cooled gargle, the quivering of the bodyshell and the idea of 400bhp pushing against just 1160kg does make me wonder. 

Get going and I really need not have worried. At idle CHI001 does a convincing impression of something fundamentally unhinged but the light clutch, gently assisted steering (there’s modern EPAS hardware in the nose) and the manners of an engine sensitively calibrated and under the heel of Motronic engine management mean this is no chuntering 3.0 RSR for the road, hellbent on living its life at 8800rpm. It pulls raucously but smoothly, with responsiveness that is fabulously sharp by today's standards but never jagged. Even the gearshift is totally insouciant. Maybe too light, in fact, but at least it is accurate and missed shifts seem unlikely.

Cross-country cruising is in general undemanding but far from unengaging, with Theon's creation exhibiting far more precision and alertness than any period 964 could muster.

Much of the transformation is down to the Tractive dampers, which are the same used by the current Porsche Carrera Cup car and are adjustable through five modes. CHI001 sits 10mm lower than a period RS 964 but in the softest damper mode its featherweight body still moves silkily over undulations while the fidelity of the steering dials you into the road. The chassis balance is also surprisingly neutral, though there's never any question about where exactly the flat-six engine is positioned. In the firmest damper mode the car is most sensitive to what you’re doing with the steering and throttle, and superbly so, but set as such the ride quality flirts with brittleness on UK roads and so even for pushing on you’re best in the mid setting. However, the main thing is that you have a choice of usefully spaced parameters when it comes to the suspension and there will be a time and place for all of them. There’s more versatility here than in the latest 911 GT3.

Confidence buffered up, you can really get to know what engine. It’s not exactly a screamer but what it lacks in higher frequencies it makes up for in sternum-buzzing intake roar and a tidal wave of waspish energy that grows inexorably towards the red line. And so much torque. It fizzes with power at higher revs and at full chat CH1001 feels BMW M3-quick – 400bhp-worth, certainly – but just as mighty is what happens when you engage another gear and drops the revs back into the mid-range. The car lunges forwards again with renewed aggression. It’s all pretty shocking for something that while purposeful also remains neat, almost demure, and agreeably small on the road. In short, usable.     

The setup is good, too. The contact patch is far bigger than this chassis would have started off with – 225-section front Michelins on the Theon are what this 964 in its original form would have worn at the back – but it doesn’t hunt about on corrugated roads like you might expect. The car's neutrality also allows you to explore the very high limits of grip and traction. Some people would I imagine prefer the car to be more transient in its handling, but if you want security and the ability to uncork this mighty engine at will, this is a fine compromise.

That said, through one off-camber corner, taken at pace and with a ridge near the apex, CHI001 does get quite severely flustered for a moment before settling. It’s a reminder that, for all its pace and panache, at speed you still have to think your way down roads in this old-spirited car, in a manner that in modern performance cars you can mostly get away without doing. But I quite like that about it. You might also want for slightly quicker steering mid-corner. CHI001 gets its friendly-looking face into corners so readily and flatly that the gearing of the rack, which is as per an original 964, can suddenly feel quite lethargic once you’re actually into the meat of bends. As with everything, you quickly adjust, but it does momentarily lessen your oneness with the thing. 

And the cost? £380,000. Or at least that is the point where Theon Design’s creations start. Expensive, yes, but considerably less than what you’ll pay at Singer, which in any case is no longer taking orders for its ‘Classic’ Porsche 911.