I just want a picture of the boys.” Hazel Chapman, Colin’s widow, lifts her camera and ‘the boys’ stop talking. Boys. Their bus passes are dog-eared now, but they were lads when they built the machine in front of us. It was 1965 when this was last in a Lotus workshop, when these boys slaved through many an April night to get it ready for the Indianapolis 500, to give Jim Clark a chance to avenge the cruel reverse of 1964. That year shredding tyres tore up an almost certain win for the Scot. A year later some of these boys were there to see Clark in his funny little back-to-front device lift the greatest prize in American racing.

From that glory moment to this, the green and yellow Lotus 38 has been preserved in the museum called The Henry Ford, virtually unchanged. It came to Goodwood last year and sat quiet and still. Now the museum wants it restored to bellow up Lord March’s drive at the Festival, and here at Classic Team Lotus Clive Chapman’s team are about to strip it to its nuts. Before that, on this chilly January day, the Team Lotus mechanics who built it 45 years ago will pore over every detail while Clive makes copious notes. He needs to know exactly what every button, scoop and tube is for so that the rebuilt car can be absolutely authentic. So here are Dave Lazenby, Bob Dance, Bob Sparshott, Graham Clode, and the car’s designer Len Terry. They’ve been chatting eagerly but they go quiet when the cover comes off the yellow-striped projectile. This thing is special to them, and to history. It flies Indy firsts like flags. First rear-engined winner, first Ford victory, first 150mph average, first foreign driver to win since 1920, first British car to hi-jack the solid-silver beer barrel of the Borg-Warner trophy. Track records lay in shreds as Clark climbed out of this device.

Part of the Ford deal was that it kept the winning car, and for 45 years it’s been a proud but silent trophy in the museum. (The car that went to two Swiss hillclimbs in 1966 wasn’t this one, despite reports.) Over the years it began to look weary, so in 2001 it had a cosmetic clean-up; that’s why the paint is shiny. But as the guys remove panels and peer inside we can see the dull alloy, faded labels and grimy corners that tell you no one has had this device apart before. Clive points out details, like the protrusions on the seat back, that confirm this is chassis 38/1. That dull red wheel is the one Jimmy gripped; that stubby gear lever the one he tugged from low to high for 200 laps. All these parts crossed that finish line together, as 200,000 people cheered and Indianapolis history turned a page.

You could argue that Chapman was lucky that the fruits on the machine clicked into line just when the jackpot was brimming: Jack Brabham had impressed with a rear-engined interloper in ’61, Dan Gurney schemed an Indy attack from 1962, got Ford on board and promoted Chapman as the guy who could deliver, while the Lotus chief had Len Terry to draw it and Jim Clark to sit in it. But luck is made of hard work, and you have to swallow some grit on the way. For Lotus it came coated in a face full of Parnelli Jones’ oil in ’63, when Clark had to concede a rookie victory behind the leaking roadster, followed by the PR disaster of ’64 and those disintegrating Dunlops. The whiff of petrol tainted the Lotus-Ford alliance, too; you burn less of it than the usual Indy methanol, so Chapman chose it for fewer pitstops – but it erupts more easily. There were mutterings that the fireball smash which killed two drivers in ’64 wouldn’t have happened if Ford hadn’t listened to that Limey, and for a breath or two the marriage looked rocky. But Chapman’s charms soon had a ’65 deal signed: an uprated methanol version of the four-cam mechanically injected 4.2 would be on its way to Cheshunt. Please build two new cars – oh, make that three. Dan Gurney reckons he’ll go it alone if you sell him a car.

At Lotus Len Terry sometimes clashed with Colin Chapman over design matters, and was happiest left alone. He doesn’t count the first Lotus Indy cars, 29 and 34, as his – merely modified 25/33s. But for the 38 he had carte blanche because Colin was out at the Tasman races, and he made full use of it to push aero design principles. Instead of the 33/34 ‘bathtub’ – driver sitting between two stressed-skin tubes – he drew essentially a single rigid hull with a hole for the pilot and two sponsons behind to cradle the V8. “When Colin came back he didn’t like the full monocoque because of accessibility. But it was too late! And I wouldn’t have changed it.” He may be slight, but Len was never one to be slighted.

Holding the wheels on was a lop-sided variant of the F1 car’s suspension – wishbones and top link up front, reversed wishbones, top link and radius arms behind, heftier discs and uprights all round. Len beckons me round the back to show how despite the asymmetry – body hunching 3in left to even out loads on ovals – the swing axle lengths work out equal for even steering response.

Pointing at the rear cross member he explains how to plot pivots to give over- or understeer as the driver prefers. “What did Jimmy like?” I ask, and he laughs. “He didn’t care! He could adapt to anything, he was absolutely brilliant. In testing you didn’t dare let him have more than two full-out laps, because by the third lap he’d have adapted to anything wrong with the car and covered it up!”

The result just looked – right. Slim, questing nose (running dope allows a smaller radiator), curved rump hiding the two-speed ZF transaxle, air-gulping intakes and those mustard tailpipes pointing skyward like ack-ack guns. A broad-shouldered cousin to the 33 F1 car.

Though he knows this car inside-out, Lazenby marvels at it. “It’s so purposeful, so right. One of the best cars ever.” Crew chief at Indy, he recalls how smoothly the long, leisurely May run-up went. “It was finished on time, and once we got to Indy there was nothing to do. We’d just push it out each day in the evening cool, Jimmy would go faster yet, and we’d put it away again. The whole month was brilliant.” Len Terry grins: “Development is correcting the designer’s mistakes. That’s why you had an easy time.”

Easy if you don’t count building up a second 38 and running Cortinas at two US races…

“How long did it take you to draw, Len?” Lazenby asks.

“Four months. I was always quick on the drawing board.”

By now Lotus had separate Indy and F1 teams but this race mattered so much to Chapman – he’d smelt the money – that Lotus forwent Monaco, run on the Sunday before the Speedway classic. So they spent all month in the USA, and loved it. Clark even had time for a quick trip to Scotland, while the Lotus crew played up national stereotypes: they all laugh when shown the picture of them in deerstalkers.

The lads don’t pay so much attention to the big vee in the back. They didn’t build that, it came straight from Dearborn. Shortly it will be sent back to the US, to Walt Goodwin at Race Car Restorations in Indianapolis. His is the tricky job of assessing how good the innards are, and what he dare keep.

Laz leans in – “I remember making those pedals!” Suddenly there are pointing fingers and a jumble of talk about breathers and fuel valves. Fuel flow was crucial to the 38: new USAC rules for ’65 meant only gravity fuelling, so to fill the tanks – two side, one behind the seat – Terry fitted a fast-flow funnel inside the rig tank and turned the one fill, one vent system into two fill pipes, increasing fuel flow by a third.

“Remember [legendary team boss] Andy Granatelli staring at the extra weld on the rig?” laughs Lazenby.

“He knew we’d done something, but he couldn’t figure it.”

“Fifty gallons in 19 seconds,” says Len with restrained satisfaction. “They all thought we’d have to stop again.” In his 80s now, Len still has a schoolboy twinkle as he recalls the tricks that went along with the science, like his self-feeding ‘bird bath’ oil tank that baffled Indy denizens by looking too small to last. They couldn’t see the back-up on the bulkhead.

The other ace in their hand was the Woods brothers (and two cousins) – drawling Southern stock car boys who manned the pumps. Famed for their pitwork, they were flown in by Ford. Helped by Len’s device, the brothers took slices out of pitlane downtime, keeping Jimmy in front for most of the race. Laz: “They spoke so slow you thought they’d never do a quick stop – but in action they were amazing!”

“We could hardly understand each other, though. They kept asking ‘You really English?’” says Bob Dance.

With these ‘unfair advantages’ lined up, Colin could safely afford to choose slower but hardier Firestones over faster, fragile Goodyears.

As more panels come off the grey heads crowd in, excited as small boys. Determined on accuracy, the museum has collated a huge amount of research material. Armed with photos, drawings and laptop video, Clive quizzes them on metal finishes, switches, instruments. He not only wants to get it right, he needs to show it’s right. CTL has drawers of drawings, but this was a race team – you modded on the hoof, and you didn’t bother drawing what you knocked up. And because you were there doesn’t mean you remember…

“Who made these?” “You did!”

There are oddities that puzzle everyone – welding stumps where something’s been moved. And “What are these four pull knobs for?” They work back into the car and into memory: “Indy made you have a fuel shut-off, that’s this one… This one’s for mixture…” Torches come out – they’re the sort of men who carry torches; Laz’s head gets further inside. It’s archaeology crossed with a logic puzzle. The collective ‘ahhhh’ when they figure out the final one – a two-gallon get-you-home tank fitted in practice – is like finishing The Times crossword.

This patch of glue in the cockpit: period or museum fix?

“Could be for padding for Jimmy,” Len suggests. “Remember I designed the car for Dan, who was much bigger.”

“One reason why Bobby Johns was a good second driver – he was the same size as Jim,” says Graham Clode.

They’d been due to run first at Trenton, NJ, but after an accident to the second car (which meant building up a fresh one under the same chassis plate) they went straight to Indiana, where stock car veteran Johns stepped up alongside Clark.

The other candidate, Parnelli Jones, ended up in his Agajanian-modified Lotus 34, while A J Foyt in another 34 and Gurney in his go-it-alone All-American Racers 38 meant that as the crowd baked and the majorettes glittered and strutted, four of the high five were Chapman cars, split by Mario Andretti’s Hawk Brabham copy.

Nine of the top 10 bore Ford blue ovals, two-thirds of the grid sat ahead of their power plants. No matter who won, after this the old order of tube frames and up-front Offenhausers was a sideshow.

Clark’s 160mph qualifier was a record-smasher, but Foyt topped it to grab pole in the older car. No matter; Clark led into Turn 1 and that wrote the script for 190 of the 200 laps.

The boys crowd round Clive’s laptop to watch the period video. Andrew Ferguson, then Competitions Manager, says in his book that Jimmy meant to trail Foyt into Turn 1, passing him inadvertently. It fits with Dave Lazenby’s comments now, eyes fixed on the fuzzy grey image. “Jimmy took two laps to settle, then he was gone.” Lap three arrives. “There, see? He’s off!” They’re all round-eyed and quiet. They were in the middle of it; they know what happened; they’re still riveted.

AJ heads Jim briefly, but those fuel stops, and the overwhelming pace of car and driver, tell. The commentator goes all Murray over the quick pitstop – surely he’ll have to stop again. “Everyone else was shell-shocked by it,” smiles Graham. The leaders trade race records, but Foyt’s stops take two, almost three times as long. Dan’s Yamaha 38 drops back – a cam gear is breaking up – leaving Parnelli Jones to hassle Foyt for second. It’s all there is to fight for. AJ is great in traffic but it doesn’t help. Jimmy has lapped everyone bar Foyt when, just after halfway, the Texan’s transmission breaks.

“You were slow with that pitboard saying FOYT OUT!”

“Yeah, I still remember the sign language coming from Laz…”

Now rookie Mario Andretti is after Parnelli, and Jones is staring at Clark’s gearbox, but dangerously low on fuel and on the wrong lap. Clark’s two-minute lead is practically the other side of the International Date Line.

“I was standing biting my nails, thinking is he going to get there?” says Lazenby. “When he made it I just felt huge relief.”

Sparshott shakes his head. “I can’t remember any of this. I was too scared!”

Tinny cheering from laptop. Crowd on feet. Chequer waves. Jim makes history, in this car right here. What was it like in the pitlane? “Euphoric,” says Graham.

“Special,” says Lazenby. “When he crossed the line I thought ‘that’s my darling!’ Your dad, Clive, leapt up to meet him.”

Clive points out that Laz is first to speak to Clark. What did he say? “Probably, ‘thank god that’s over. Where’s the money?’” Everyone laughs; Jim did enjoy the cash. For this one win Clark collected £46,000. In the same year his F1 World Championship brought him £13,340.

“There’s George Bignotti. He came to Colin and asked ‘how much did you win?’” Over $166,000 is the answer. On screen the onlookers surge, Jim holds up the newspaper and drinks the milk. Hazel is proud that despite the men-only tradition she and Clark’s girlfriend Sally Stokes pushed into the winners enclosure. “They weren’t going to keep me from that!”

And all America watched; this was the first time the 500 made national TV, so Ford’s cup overflowed. Eight of 11 finishers had Henry’s V8s; the marque would dominate Indy for the next six years. Of course, a US driver would be even better; Ford decided to back Gurney’s AAR-Eagle affair, and Len, already working out his contract, went with him to build an even more beautiful machine. Meanwhile everyone wanted a 38 and while No82 went off to begin a show tour at the New York World’s Fair, Chapman plotted a production line. But the tub was complex to build; the various Teams Lotus were stretched. Just two customers – Foyt and Andretti – got 38s, built elsewhere in different alloy. Known as the Soft Alloy Specials, they weren’t successful, and comments about them still make Len bristle.

“They weren’t more flexible, they just weren’t as strong. People don’t know the difference. They don’t understand.”

All this was in winter, before the strip-down. Lotus designer Martin Ogilvie checked the tub was sound; Ford historians went over Clive Chapman’s comprehensive report deciding line by line how to treat each part so it would look just – no, be just as it crossed the line. Then the Classic Team Lotus crew under Lewis Cullington got going (even they retain one original component – Bob Dance, with his comprehensive notes of everything he did). There’s also the racks of drawings, photos and old-new parts preserved from Team Lotus, not to mention the wide-ranging skills, which make this the right place to bring your 38 for its first 500-mile service. It’s in good company: they’re also working on a 94T, 97T and another Clark treasure – the 1967 Dutch GP-winning 49, Chapman’s Next Big Thing.

Many of CTL’s restorations are for racing, which demands fresh components. This is different. Originality was paramount. Over the years the front lower wishbones got bent being tied down by over-eager truckies, so for safety there are fresh ones, plus new hydraulic lines, and to preserve the real things there’s a stand-in seat and steering wheel. That’s all. Even Graham Clode’s wiring is retained, after checking. But the Henry Ford plans to run the car only at Goodwood and possibly at Indy; after that the straightened 1965 wishbones and Jimmy’s seat and wheel go back. It’s the same with the motor. Once Walt Goodwin got it apart he was able to re-use even pistons, pins and bearings, knowing that no one is going to be hitting the red line with this V8. Replacements were limited to trivialities like O-rings. This machine is original. And seminal. Not only a winner of huge significance, this car sired a line of Indy success, including Gurney Eagles and A J Foyt’s Coyotes, and altered the vocabulary of racing car design.

Though ‘82’ will also go to Pebble Beach, the museum forbade shiny show flourishes; it had to look transported by Tardis from May 31, 1965. And, boy, does it. Once Jackie Stewart has brought it back to the Goodwood paddock, if you can push through the crowd, check the decals on the deep green cellulose (matched to original paint found inside) against the photos. Or the cable runs. Or any of a hundred tiny details. It’s gorgeous, sensitively restored by people who care about getting it right. This is one of racing’s great cars, exactly as it was on one of racing’s great days.

There’s only one thing wrong. It needs 500 miles of grime on it. That’s 431 runs up Goodwood hill. Jackie, start your engine.