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Which Kit? article

Sienna - Short but sweet

After several years of intensive development, Sienna cars finally got it’s Countach replica pretty well sorted out by early 1991. Then, just as the future was looking bright, the company suddenly folded.

As with most Countach replica’s, the Sienna was developed from an earlier example of the breed. In this case it was the Prova, although it is very likely that the Prova came from Venom etc., etc. A guy called Alan Booth was the man responsible, and little could he have guessed that, as he founded a business building up Prova’s for other people, that he would end-up creating a car which some reckoned was better then the original Countach! Alan Booth, a New Zealander, wandered over to the UK for a holiday in 1986 and, instead of going home again, had become involved in the kit car industry. He used to be a sheep farmer, so obviously the next step in his career had to be making Italian replica supercars. It’s what most New Zealand sheep farmers finish up doing ultimately! Actually, he had also been involved in oil pipeline technology, but after a few years of constant airports and relentless pressure, he’d wanted to get into something with an element of pure fun in it.

Alan had at the time never heard of the Lamborghini Countach, although he was quite familiar with Lamborghini tractors. When he first came face to face with a Countach, he was gobsmacked. Having got past that reaction, the next stage was: "I must have one!".

At that time the Countach replica industry was in it’s infancy, and it took all Alan’s engineering skills (and knowledge of sheep?) to complete his first build, a Prova of course. Offering his services through the kitcar press, an order or two materialised and premises were taken on a run-down farm industrial estate at Ranmore Common, near Dorking, Surrey. A show appearance brought more orders and suddenly Sienna Cars was fully viable. Trouble was, Alan knew he could do better then the Prova...

With funding provided by a wealthy customer, developement of the Sienna Countach proper began. A new chassis, new body moulds, fully revised suspension, an improved interior, easier production facilities – the car got the lot. It also got a new home. Still very rural, and this time on an old army storage depot at Sutton Veney, near Warminster, Whiltshire.

Thousands of development hours, plenty more funding, further improved moulds and much company restructuring later, and the car had matured into something rather special. By spring 1991, with a small number of kits already supplied, the Sienna Countach was receiving wide acclaim. Which Kit? magazine was full of admiration:

‘The Sienna one of the worlds fastest, most exotic sports cars? Of course. The car is an absolute credit to the whole kit car industry. We’re happy to say that the Countach replica has truly arrived.’

Little could the magazine have predicted the brevity of the euphoria.

All in all, the Sienna Countach was a pretty serious piece of kit. The exterior dimensions accurately replicated those of the real Lamborghini, although inside there was more headroom and some 4” more legroom. Powerplants were variable, although one of the favourites was the 302CI Ford V8, with the smaller Rover V8 as another option, and the occasional Chevrolet 350. The Renault V6, fitted with the Renault gearbox wasn’t a bad option either: quite a good unit and quite tunable.

An unusual engine at one time fitted to the demonstrator was a Cosworth 2-litre turbocharged Ford Pinto unit: However, it didn’t sound right or feel right, so it was replaced by a Ford 302. At one stage, the Jaguar V12 option was under development, but posed large problems – gearboxes and all that. The Renault 30 unit, used in most Countach replica’s, just wasn’t up to the job of coping with the V12’s creamy, limitless power.

The chassis, made in-house, was an advanced multi-tubular spaceframe with an integral roll-over bar. There were nice touches in it, such as an extra bearing designed into the steering linkage for extra smoothness and precision, and in the engine compartment a bolt-on brace bar to make engine and gearbox removal easy. With new jigs, tolerances were down to 0.5 mm, which was close enough for anybody.

Suspension was independent all round via double whishbones, coil-over schock absorbers and Ford Scorpio hubs and uprights. The steering and a full set of disc brakes were also Scorpio, all chosen on account of their design quality and worldwide availability. There was no doubt about the thought invested in the layout.

Wherever possible, computer aided design and laser cutting techniques were used. The grilles around the car were a visible sign of this: they were laser cut steel, powder coated. They were perfect, end of story. The Sienna designed suspension parts were also laser cut, where they weren’t castings. Where they were castings, there was some clever stuff going on. Rose joints were used in the suspension. Aha! Might one think, that means a horribly brutal ride, and they wear out in 10 minutes!

Well aware of that, Sienna enclosed the rose joints in rubber boots, filled with grease to keep the grit out, and mounted bushes in the castings to keep the ride civilised as well as gaining the precision suspension provided by rose joints. All clever stuff!

The same blend of sharp handling and a reasonable ride was followed in the shock absorbers, made by AVO for Sienna. The system was set up with a corner weight facility, and with the adjustability inherent in the rose joints and the shock absorbers, the suspension could be tuned to suit pretty well anyone.

Turning to the nicely moulded body (with bonded in steel reinforcement to increase upper body rigidity), there was curved, laminated, tined glass throughout, provided by a local company. The windscreens themselves were supplied by Triplex. The GRP bodywork was massively solid: the front bonnet was hard to pick up by hand, and it was by no means a big panel. The engine radiators, mounted behind your shoulders, were large locally made items, very effective indeed. The twin fuel tank fitted under the radiators were made in aluminium by Sienna, filled with Explosave.

Arches, front spoiler and so on, were bolted on seperatly, like the original car. Something that we never saw on any other Countach replica. With as extra benefit that these items could easily be replaced if damaged. Sienna even advertised with providing every customer with a free front spoiler per year.

Laser cutting again reared it’s head: the tail reflectors were cut this way, and they fitted perfectly. Likewise, the dashboard blanks, available in plywood, steel, ally, veneer, anything you liked. What would normally constitute literally a full day’s delicate work with drilles and files, took the machine 0.92 seconds.

The car was intended very much to be a practical every day vehicle, and the demonstrator was deliberatly used that way in order to make the point. As well as being trashed around the place by every journo in the world and by hundreds of potential buyers, it was used by Alan Booth as an every day car for work shopping, and had no other attention other than frequent washing. The engine bay was defenitly that from a working car, and a noticeable advantage was accessability. While access will never be easy in a car this shape, it wasn’t bad at all in the Sienna.

The luggage boots, one at each end, held a reasonable amount, and the cabin was spacious., with lots of sprawling room particulary for the passenger. The windows on the demo car were fixed, as interior cooling was by an air conditioner fitted in the front boot. All smart stuff.

In action, the Sienna was equally smart. Clambering in was as akward as with any Countach but at least the doors shut with precision. The dark blue demo car’s cabin was laid out in original style and beautifully trimmed in light grey leather. Though the seats needed adjusting for the individual driver, the driving postion was basically spot-on and the controls all well sited.

The menacing yet comfortably muted rumble from the 260 BHP Ford 302 V8 sounded great. At cruising speeds, the car was docile, the power unit lazyliy comfortable; if you wanted to use a little more muscle on the accelerator, the Sienna’s engine provided more muscle itself and urged the great thundercar forwards. With the carburettor’s second choke operative, the whole experience was exhilarating, the acceleration relentless.

Ride was amazingly supple and comfortable for a car of such proportions. Steering was pleasantly light yet retained the sort of feel a supercar driver would need, it only became heavy at low speed. With the gearshift accurate and precise and the braking pleasantly progressive, the whole experience was a delight. The Sienna handled with precision and gripped abundantly. A little old British kit car performing like a classic Italian supercar? You bet!!

So, the car worked a treat. It was engineered superbly and blessed with excellent quality body panels. A steady supply of kits was being made at the Sutton Veney workshops  and the future was looking bright. Alan Booth has said he wanted to be known as the producer of the world’s best Countach and he was getting there! Wheter you paid arounf 7500 gbp for a body/chassis kit or some 35k pounds  for a fully build car, you were getting something quite special too.

Problem was, you didn’t have very long in which to get it. From the point when Which Kit? stated, in May 1991, that the Sienna was ‘probably the world’s best Countach replica’ the company only lasted another few months. By early 1992, Sienna Cars had gone bust with remarkably large debts. More confirmation of how financially dangerous it was to attempt full-scale development and production of one very complicated motor car. Even what was considered to be the best example of the breed, had failed.

No more then 25 Sienna Countachs are believed to have left the factory, in kit, semi-complete and turn-key forms. Not much of a total considering the car’s quality and capabilities, but enough to ensure that it won’t be forgotten.

Several of those 25 cars were shipped to various parts of the world and appreciation will no doubt be the same in every language...

This article was published in the Which Kit? issue "Italian sportscars".
With kind regards to Which Kit? for giving me permission to re-publish this article.