Marcos Mantis XP – the wildest car ever to come out of Wiltshire

| 10 Feb 2014

'New Le Mans Marcos Mantis!’ So proclaimed no lesser a news source than The Bath Chronicle in early 1968. It continued: ‘Although completed too late to go to the Le Mans test days, the new Group 6 Marcos sports-prototype is now in being.’ It might not be in the sensationalism league of a national red-top, but you can’t blame a parochial rag for getting excited about an enterprise on its patch building a car that promised to take on and beat the world’s finest endurance racers. Particularly when Marcos already had an enviable record at La Sarthe. Except that, although the car did exist, its assault on those big-name marques never happened. Instead, this unicorn of the breed raced just once and disappeared, earning itself a place in motoring folklore as a result.

So it was all hype, then, a publicity-garnering exercise from Wiltshire’s most durable cottage industry? No, quite the opposite. Some 41 years later, the Mantis XP (for Experimental Prototype) finally reappeared in the UK and enjoyed a rapturous homecoming, its fascinating story unfolding in the process.

The car was indeed built for Le Mans, and was intended to be a serious contender before going on to contest the World Championship. Styled and built upstairs at The Forge by the Adams brothers, Dennis and Peter, with Stan Gray and others, it used a glassfibre body over a traditional – for Marcos – stressed-plywood tub, with steel-tube front and rear subframes, and the fuel held in side pontoons. The intention was to use a rear-mid-mounted BRM V12, but that proved traumatic. As Marcos founder Jem Marsh explains: “They wanted huge piles of cash and then couldn’t get their act together in time. So, over a Chinese meal, I bought a Repco from Jack Brabham instead.” The Rover-blocked 3-litre Brabham-Repco 740 V8 was mated to one of Mike Hewland’s DG300 five-speed transaxles. To continue the F1 theme, Marsh bought in a complete all-independent suspension set-up: “I just rang John Cooper and asked if he would sell me last year’s F1 suspension, and he did.”

When the Mantis was finished, they had to cut a hole in the floor to drop it out of the Bradford-on-Avon workshop. It was an ignominious start for an astonishing car.

Everything looked rosy until things kicked off in France. With civil unrest rife across the country, the 36th Grand Prix of Endurance was postponed from its traditional June slot to mid-September. By then, the Marcos Mantis XP was on the other side of the world. The car had raced, just once, at Spa-Francorchamps in May. It had a good turn of pace but, in torrential Ardennes rain, the cabin quickly began to fill up. The car came in and holes were cut in the floor to let the water out, and, having restarted at the back of the field, by lap 10 the XP had climbed to 21st of the 38 runners. Eddie Nelson’s spin at La Source pushed it back five places, but two were regained before the Marcos hit a major problem. The alternator, slung out of the back of the car as was the norm with mid-engined racers, was sodden and there was a major misfire. Desperate to preserve the engine, Jem Marsh called a halt after 13 laps and the team went home: “We didn’t have the money to risk blowing up an F1 engine and it had been a pretty miserable weekend so we called it a day. The car went very well and the chassis was excellent, but I wasn’t even meant to be driving – someone pulled out at the last moment and we took out all the upholstery so I could squeeze in. There I was in this horrible weather, in a car I’d never driven in vengeance, not able to see a bloody thing in the rain, head cocked to one side because I didn’t fit in the car which was built around Peter Adams, a GP engine up my backside, sitting on the floor in a puddle of water. I don’t think either Eddie or I was too upset at stopping.”

Back in the UK, the Repco was replaced with a Buick V8 “that was lying around” – the engine the Rover unit was derived from in the first place – and Marsh took to driving the car on the street: “The old ladies of Bradford-on-Avon thought it was something from another planet. It was quite enjoyable really.” Then the trouble started. Because the Mantis was being run on the road, Her Majesty’s Customs and Excise started demanding that Marsh pay Purchase Tax on it. A lot of Purchase Tax. “They put their own huge value on the car and based it on that,” says Marsh. “It would have been a vast amount of money to us and the only way to avoid paying was to export it. I had a contact in America, so off it went.”

The XP appeared at a couple of shows before it was snapped up. Then things went quiet for a very long time. Contrary to popular belief, however, the Marcos didn’t disappear into a private collection or museum. Californian enthusiast Tom Morris and his family saw the XP at the LA Auto Show in 1970 and had to have it. A crucial part of the deal was that he could drive it on the roads, so when Morris bought the Mantis he insisted on meeting the seller at the local licensing office and only handed over his money (memories are hazy, but it was between $5000 and $7500) when he got the papers that made the Marcos street-legal. The XP has been with the family ever since, ownership passing to the four sons – Ned, Chris, Pat and Drew – in 1986. They endeavoured to keep it on the road so, when emissions controls reached their height, the family re-registered the car where Ned was studying so that it could continue to be run as LA’s ever more stringent smog laws came in. 

“My father used to take me down Topanga Canyon and Mulholland Drive in it,” says Ned. “The furthest he ever drove it was Monterey – that’s when he had the 8-Track installed.” In the 1980s, Ned started to use the car to take his friends out and to lark around. Mother Roberta chimes in: “Chris was the first son in the driver’s seat, though! If your father took his Mangusta or Sebring, or whatever he was using at the time, to work, then I used to take the Marcos to go down to the store and do my chores when I was pregnant with Chris. I always called it the ‘happy car’ because when you went past people they would snap round to look at it, always happy.”

The state of the car, still sitting on its original Dunlop rubber, started to deteriorate – “for years it didn’t have fourth or fifth gear,” says Ned. It was he who decided to do something about it, prompted by increased interest in the XP following an article in Torque magazine in 1989. Ned made a start after finishing a Camaro restoration early in the new millennium, and went public in 2004. “I’d wanted to do it forever, ever since the early ’80s, but didn’t get around to it for all sorts of reasons,” he explains. “I bought a new house with a three-car garage and nothing to fill it with, so I brought the car up here, got it going and started taking it to track days.”

The XP appeared at nearby Thunderhill Park and a couple of local car shows. Taken aback by the overwhelming reaction, and alarmed by the state of the never-restored 40-year-old car, Ned decided to fettle it a bit: “It started out just as doing the engine. Then it was the transmission and the suspension, and pretty soon that developed into a full restoration.” A house-builder by trade, Ned has done much of the work himself – up to and including the trickily curved Perspex windows. The intention was to ready it for Monterey 2009, but when contacted about the Marcos half-century celebration the same weekend at Prescott Speed Hill Climb, he switched his focus. Even then it was a close call, and Ned was still putting the finishing touches to the XP as the shippers arrived to take the car to the UK, funded in part by donations and sponsorship.

C&SC caught up with the XP fresh off the plane at Marcos Heritage just prior to the event on 16 August. Even today, the Adams’ work is a visual sensation: that truncated Kamm tail, the inverted arrowhead shovel of the front end – complete with ingenious suitcase tray to satisfy Le Mans regs – with the headlights frowning out of the wings. And, in the middle of it all, the McLaren F1-like cockpit, nearly all transparent so it really does look and feel like a plane. 

It even feels futuristic on the inside but, once you have clambered over those super-wide sills, it is surprisingly comfortable – though perhaps less so for 6ft 4in tall Jem Marsh. Given its all-Perspex hood stretching down to the sills, it is unsurprisingly airy despite being relatively narrow. There is a definite familiarity for anyone who has ever sat in a Probe, but this has a varnish of hard-nosed practicality. The inside of the Perspex above your head is painted black, with a gap to allow you to see the roof-mounted mirror. The bank of dials is misleading as you notice that three are oil temperature gauges, of which just one is operational and probably none are necessary given the superb airflow through the nose-mounted oil cooler. In front are a 240mph speedo and an 8000rpm rev counter, plus a row of switches. The latter seems a little redundant, however, because once strapped in nobody apart from Stretch Armstrong could reach any of them. Just one twisting stalk is accessible to the diver’s fingertips and that flashes the lights to warn slower vehicles to get out of the way. Its maker’s priorities – and confidence – are obvious. The three-spoke sports wheel, on the other hand, protrudes well into the cabin on its fixed column, which means that the pilot can assume a comfortably reclined driving position. 

It didn’t take long for us to decide that the natural place to take the car was Castle Combe, where it was tested in period. Ned had no qualms about driving the Mantis to the circuit on the road – “Hey, it’s insured” – though other drivers looked less convinced as the spectacular racer cut its way through Chippenham, causing countless jaws to drop. With only a one-hour lunchtime slot to exploit – and that thanks to the generous Porsche Club Track Days organisers – our first run at Castle Combe is frustratingly slow behind a camera car. Towards the end of the session, however, there is an opportunity to see what the XP can do over a couple of laps.

To start, flick the twin switches for the SU fuel pumps, then the ignition switch, and press the button on the central tunnel. Even with just Supertrac cans it seems quiet for a hot V8 wearing an eight-branch manifold. And, despite a quartet of downdraught Weber 44s in place of the original four-barrel Holley, a trick cam and forged pistons, the 3½-litre Buick V8 struggles to match the power the Brabham-Repco must have had. Yet Ned’s efforts to work it back up to some 250bhp-plus are definitely worthwhile. By ignoring a couple of flat-spots and keeping your foot in, it soon works up to an easy – indicated – 120mph by Avon Rise with little drama. There the Marcos – as does everything – lightens considerably. And it does feel like a very light car: not as light as
the 650kg mentioned in 1968, perhaps, but nowhere near as heavy as the 1285kg stated on the recent air-freight documents. 

After Avon, it is all hard braking before Quarry. With Girling discs all round, stamp on the pedal too hard and you will stop the car dead even from that speed. Gauge it right, however, and you have just the right momentum – and lack of weight transfer – to hurl it into the corner and cut square across the apex. Quarry is a difficult corner, normally, but the flex-free Marcos dismisses it with disdain. Flat and neutral, it spears through with no loss of grip from the Dunlop Racing tyres – 4.75x10 at the front, 6x12 to the rear on 15in four-bolt wheels – as you simultaneously straighten the wheel and bury the huge throttle pedal on the exit. 

The Chicanes weren’t here in 1968 and it is on the first of them that the XP gets out of shape, the tail sliding, but it’s easily held and corrected before you can put the power down again. The steering is beautifully direct and it’s super-responsive when it loads up, that wheel a perfect arm’s stretch away for guiding it through Le Mans’ Porsche Curves. We can but dream.

It’s fun (and sometimes a challenge) to bully the XP through the straight-cut gears using that sill-mounted lever. Yet the truth is that the engine is so tractable and the gearing so long in that dog-leg ’box that you could drive this entire 1.85-mile circuit in second or, because it’s someone else’s engine, perhaps third. There is no need to be too cautious with that low-slung V8 because it is freshly and well rebuilt. Radiators with thermostatic fans in the huge side-scoops keep it close to a very reasonable 85˚C, the sliding Perspex windows and single eyeball vent doing a similarly efficient job of airing the driver. Oil pressure is steady between 60 and 80psi.

Contrary to some period reports, Marsh is adamant that, while racing success might have led to a few more XPs being built, it was never his intention to put the XP into production. That doesn’t stop it being very roadable. To look at this comic-book shape and hear its V8 bellow, to manhandle that transaxle and stare through the roof to see what’s behind you, you might not think that this is much of a road car, but using it as one is far from unfeasible. The ride on the all-independent suspension is hard, but no harder than a modern Evo Think-of-a-number and those well-padded seats, nicely shaped and slung deep into the chassis, make it a surprisingly pleasant place to be. In fact, unlike with most Le Mans racers, it’s easy to imagine enduring 24 hours taped into this missile and emerging without feeling that you’ve inadvertently spilled Mike Tyson’s pint and suffered the consequences. There’s even a footrest cut into the tunnel.

Huge credit to the Morris family for quietly proving over 40 years that – deliberately or otherwise – Marcos built probably the world’s first road-legal and genuinely usable F1-spec sports-prototype. Shame on those bureaucratic jobsworths whose usurious Purchase Tax demands put the kibosh on the project in 1968.

This article originally appeared in the November 2009 issue of Classic & Sports Car magazine, which retains the copyright to all words and images. Click here to see our terms and conditions. 

Words: James Elliott; pictures: James Lipman