Is there a better sports car for both road and track than the Caterham 7? Chris Rees doesn’t think there is – and here’s his guide to improving yours

When Colin Chapman designed the Lotus 7 – something he said he did “in a weekend” – he intended it to be a car you could drive to the race track, win on the circuit, and then drive home in. Some 57 years later, the 7 is still going strong, and still doing much the same thing – except these days you’ll probably drive it to a track day, humiliate everything else on track and then blitz home with a huge grin on your face.

It’s fantastic straight out of the box, but how easy is it to make it even better? Once again, the 7 has a hand in spades: it’s ultra-simple to work on and has fantastic back-up from the factory and from specialists.

CHOICE OF MODELS

It’s important you get the right car to suit your needs – not always easy as there are almost as many varieties of 7 as there are cars built (my book, Magnificent 7, details every version built by the factory – over 80 of them!). Even the most basic standard 7 is going to provide fantastic performance. Although the 7 has developed hugely over the years (so that not a single component remains from the Colin Chapman-designed Lotus 7), the changes have been evolutionary. An interchangeability of parts makes the 7 tremendously adaptable to worthy upgrades but do so with some thought.

HOTTING UP

Perhaps the widest degree of choice comes in the engine department. Recent Caterhams (2006 on) have mostly switched to Ford Sigma and Duratec power, but older 7s might have any of a huge selection of Rover K-series, Vauxhall, Ford Kent and Lotus Twin Cam power.

A basic 1600 Ford engine is quite sufficient for a bit of fun at weekends but Caterham’s Ford Supersprint version (135bhp) or Cosworth BDR (up to 170bhp) were classics for performance die hards.

The Vauxhall Astra-powered HPC offered a minimum of 165bhp in the 7 and has tremendous tuning potential. Note that turbos are generally a no-no in 7s. There’s precious space to fit one under the bonnet and problems of turbo boost in such a light car are notorious. If you’re doing trackdays, catalyst bypass pipes and larger silencers are available from Caterham. TWIN CAM The Lotus Twin Cam 1558CC engine (latterly made by Vegantune) is a classic, but build quality and reliability was always variable. If neglected, power and performance can drop significantly and the cost of overhauling a Twin Cam is much higher than any of the pushrod Ford units. The good news is that parts supply is better than ever and you can build engines that are superior to when they were new, says Burton Power.FORD PUSHROD The choice for most 7s from 1980 until the mid-1990s, the Ford crossflow makes a practical and reliable choice, with plenty of spares back-up and masses of tuning potential but reliability can suffer as a result. Caterham made its own tuned Ford units in the Sprint (100-110bhp) and Supersprint (bored out to 1.7-litres,135bhp), which are reliable and worth seeking out.

COSWORTH BDR A gorgeous engine, if somewhat temperamental. In 1600 form, it had 150bhp, or 170bhp in 1700 guise. Weeping head gaskets were a problem even when new, and constant adjustment is needed to keep these highly tuned engines in the peak of performance.

VAUXHALL The Astra GTE 2.0-litre engine fitted from 1990 is a superb high-powered engine: reliability, spares and servicing are all very easy. Even in its least powerful guise, as extracted from a standard Vauxhall Astra/Calibra, it offered 165bhp, while Caterham offered ‘Evolution’ upgrades to 235bhp or, in JPE guise, a whopping 250bhp. Plenty of specialists can do the same thing – and indeed go even higher.

ROVER K-SERIES Offered from 1991 until 2008, the K-series was the engine to have in a 7 for many years. The standard Rover Metro 1.4 GTi may only have kicked out 103bhp but developments were many: 1.4 Supersport (128bhp), 1.6 (115-135bhp), 1.8 (122-140bhp), 1.8 VVC (150-165bhp), 1.8 R300 (160bhp), 1.8 R400/VHPD (up to 200bhp) and 1.8 R500 (230-250bhp). Much has been said about the weakness of head gaskets in K-series engines, and highly tuned K-series powerplants are perhaps less favoured these days.

FORD DURATEC From 2005, Caterham offered the Cosworth Duratec 2.3 (CSR) with 200-260bhp, and the 2.0 Duratec with 170bhp, right up to 263bhp in R500 guise. This is the ultimate engine, tuned with the help of Simon Armstrong of Ultimate Performance. Caterham itself offers engine upgrade packs – for instance, a pack to upgrade the Duratec 175 to 200bhp costs £1440, and the R300 175bhp to 220bhp is £2274.

FORD SIGMA From 2006, the entry level engine has been the Ford Sigma 1595cc unit with 115-150bhp and this is a great starting point. The Suzuki 660cc unit (just launched) takes the 7 back to an era of much lower power outputs.

NON-STANDARD ENGINES One of the joys of the 7 is that virtually any engine can in theory be fitted. Although the factory does not recommend alternative engine choices, drivers fit all kinds of units: Alfa Romeo, Toyota twin cam, Mazda rotary, Ford Zetec, even Rover V8. Beware of the weight difference of alternative engines upsetting the handling balance, and you need to make sure of the soundness of areas like engine mounting points, rear axles and suspension.

HANDLING THE POWER

CHASSIS There are essentially three types of Caterham chassis: the original S3 ‘imperial’ chassis, the revised and strengthened ‘metric’ chassis (from 2006) and the quite different CSR series (from 2005). The first two were available optionally in wider SV form, the latter only in SV size. If you’re a wide driver, the SV chassis is best; if you’re tall, make sure you have a Long Cockpit 7 (standard from 1992), while a very popular upgrade is Caterham’s floorpan lowering kit to provide extra room.

Lotus expert Barry Ely says most owners set their cars up far too hard. He prefers a bit of movement in the springs as it makes the car more manageable in the wet and has track victories to prove it.

Throughout the 1980s, most Caterhams had a Morris Ital live rear axle but Sierra-based de Dion rear suspension (available from 1985) is to be found on most cars. If your engine has more than 150bhp, live axles are not ideal; the unburstable de Dion rear end can handle very much higher power outputs. If the rear A-frame still has rubber bushes in it, consider upgrading to harder ones to improve handling sharpness but poly bushing may be too unyielding.

Aero-form wishbones, as fitted to the Superlight R500 from 1999, are a popular upgrade on other 7s, costing £729 from the factory, while a limited slip differential (standard on Superlight and Supersport models from 2008) is a worthwhile option if you have a lot of power under your right foot. Rear disc brakes (from 1988), honeycomb side impact protection (1990) and Bilstein suspension (1991) are all significant advances which enhance the appeal of the 7. Ventilated disc brakes and four-pot callipers have found their way on to the Caterham price list in recent years, as have Eibach springs and dampers derived from the C400 race series, and are a popular option. Wider-track adjustable front suspension is also a good upgrade to consider, while thicker anti-roll bars can sharpen up cornering too.

GEARBOX Five-speed Sierra ’box (from ’86) gives far better cruising ability. Changing the ’box on K-series and Vauxhall-powered models is awkward, as both have special bell housings in aluminium. Caterham’s own six-speed close-ratio unit enhances acceleration and upgrading to this costs around £2500. There’s another choice these days, too: a Caterham Motorsport six-speed sequential, derived from its racing programme. An ultra-close ratio ’box, it’s 10kg heavier but provides lightning-fast changes. It’s an extremely pricey option, though, at £7200, and can only be fitted to 7s with a metric chassis, or any SV/CSR.

BODYWORK Less is definitely more with a 7, and weight loss is on the minds of most owners. The best seats to have are lightweight composite, carbon or Kevlar. A windscreen is essential for road use but you can get away with an aero screen on the track. A Momo quick-release steering wheel with integrated indicator switches makes a lot of sense, too. If you’re doing a lot of track work, consider a trackday rollbar or full rollcage and a proper racing harness.

RACERS Buying an ex-racer can make a lot of sense, and make ideal choices for the driver who plans to use the 7 primarily for trackdays, sprints and hillclimbs – plus they also tend to be a little cheaper than their road-going equivalents.

Be warned! Virtually all racers will have had some sort of shunt in their career, however. The good news is that chassis repairs are quite feasible with the 7 and it’s really the quality of the fix that you should be concentrating on.

Many ex-racers make their way on to the road once they are retired from active service. You will probably want a passenger seat and some interior trim for ‘comfort’ reasons while you may want to remove the battery cut-off switch and that intrusive full race roll cage for similar reasons. Dedicated racers such as the Superlight series cars are not required to be road legal, so converting them for the road is more involved. One advantage of ex-race cars is that often they have a higher specification than road cars. You pays your money…

New entry-level Caterham 160 is an exciting new arrival with a real ‘old school’ look and power courtesy of the jewel-like Suzuki 660cc three-cylinder engine. It’s a tiny little unit normally used in a Japanese domestic Jimny, taking advantage of the tax-breaks given to ‘Kei’ or city cars.

It’s been tuned by Caterham to better suit their purposes although it still produces just 80bhp. They haven’t stopped at the engine either as they’ve plundered Suzuki’s parts bin for differential, live (yep, LIVE) rear axle, brakes and a bag load of other bits and pieces.

This includes hubs and skinny 145 x 70 R14 wheels, meaning they are specific to the 160 and much like a ‘Q’ plate means they can’t be changed for bigger, lower profile rubber. When you see them, they look incredibly narrow, more like an Austin Seven rather than a Caterham Seven. I guess that it’s a sign that times have definitely changed when even Granny’s humble shopping car wears 205 x 45 R18 tyres.

I have to confess that I’d been looking forward to driving the 160R since it was first announced, perhaps, whisper this, even more than the incredibly powerful 620R. Er, maybe not, but a close thing. Two polar opposites but equally attractive. One thing’s for sure, the Seven with the 660cc engine won’t cost nigh-on 60 grand. Far from it. The 160 comes in at £17,995 (delete £3000 if you want it in component form and as such replaces the old Classic, which latterly wore a crisp and quick K-Series 1.4-litre engine.

BEST OF THREE (CYLINDERS)

Out on the road, the 160 is a laugh a minute hoot. As mental as the 620R but in a different way. Very much its own way. The turbocharged Suzuki has only got 80bhp and produces a similar amount of torque, although it’ll despatch the 0-60mph sprint in just 6.5-seconds, helped, no doubt, by the fact that it only weighs 490kg. The car’s interior is also suitably spartan and the cloth-covered seats are entirely right, although you can upgrade to leather, if you prefer.

The old Classic model was what it was. An entry-level Seven that wore its badge with pride but let’s be honest left you wishing that you’d saved the extra bit of money and gone for the Roadsport that didn’t have balloon tyres and would be more desirable when you sold it.

Not the 160 though. It’s going to attract buyers because it’s brilliant. The sub-18K price needs looking at though. If you tick option boxes for items you’ll definitely need such as ‘irrelevances’ such as weather equipment (it rains!) at £1250, lowered floors at £395, carpets at £115, leather seats at £500, a Momo steering wheel in lieu of the standard Moto Lita items at £300, a heater at £300 and oh, paint (choose from one of six standard colours) at £1150,  you’ll rack that price up to £21,708 (£18,708 in kit form).

For purists, it’s manna from heaven. In an age where we’re used to Caterham Cars giving us ever more powerful and sophisticated versions of the Seven, the 160 couldn’t be more stark if Caterham had announced a Ford Crossflow-powered version and Peter Capaldi isn’t the new Doctor Who, it’s actually Jon Pertwee. We’ve stepped back in time, to a simpler and less complicated age, although when you look closely the 160 is actually extremely clever and full of trickery. Exquisite stuff.