Production
Director John Frankenheimer later said when he made the film he had the "choice of making a Grand Hotel type picture or a Test Pilot type picture" and he chose the former. Swedish actress Harriet Andersson was originally cast as the female lead, but was replaced by Eva Marie Saint after the first week of filming.
The making was a race itself as fellow Hollywood icons Steve McQueen and John Sturges planned to make a similar movie exploring the life of racers, with the McQueen/Sturges team initially using the title Day of the Champion. Due to the McQueen/Sturges production's exclusivity contract with the German Nürburgring race track, Frankenheimer had to turn over 27 reels shot there to Sturges. Frankenheimer got ahead in schedule terms anyway, however, and McQueen's project ran into a wide variety of financial and other problems, causing a five-year delay until the 1971 release of the retitled film, Le Mans.
The production team began by using connections to Grand Prix drivers such as Dan Gurney, Carroll Shelby and former Grand Prix World Champion Phil Hill, who all assisted them in trying to break through an otherwise reluctant European establishment. The filming process meant disrupting vital practice runs and otherwise getting in the way of the actual racers' activities. The Grand Prix team initially faced a particularly lukewarm response from Ferrari, with the firm concerned that the movie would overly sensationalize their work. Frankenheimer spliced together approximately thirty minutes of detailed footage after filming in Monte Carlo, temporarily halted the movie's production, and sent the short piece over to the company's management. He received such a positive response that he gained unprecedented access, being allowed to shoot inside Ferrari's production floor alongside the real racing vehicles. The director used this budding relationship to push other entities to help with the film-making process. Many real-life drivers of the era ended up making cameo appearances in Grand Prix, several even briefly speaking alongside the actors.
The F1 cars in the film are mostly mocked-up Formula Three cars made to look like contemporary Formula One models, although the film also used footage from actual F1 races. Because Yamura Motors is a fictional race team, the producers struck a deal with Bruce McLaren's newly formed McLaren team to have his car, the McLaren M2B, painted with Yamura's colors. The paint scheme used was designed to resemble that used on the contemporary Honda RA272 cars competing during this period. On two occasions, because the McLaren could not take part in these races, another car was painted in the same colours: Bob Bondurant's BRM at Spa, and at Zandvoort for the Dutch GP, the Lotus 25 BRM entered by Reg Parnell for Mike Spence.
Some of the footage was captured by Phil Hill, the 1961 World Champion, who drove a modified camera car in some sessions during the actual 1966 Monaco and Belgian Grands Prix.. Notably, several aftermaths of incidents from the Belgian Grand Prix were shown during its sequence, but the aftermath of Jackie Stewart from his crash at the Masta Kink was not shown. In order to realistically film the racing cars at speed, the camera car used for much of this filming was a Ford GT40, a fast and powerful endurance racing car of the same type that dominated races such as the 24 Hours of Le Mans during the last half of the 1960s. This was some of the earliest experimentation with in-car cameras for F1, particularly in terms of first-person shots aimed at putting the audience in the position of the racers.
The actual level of driving ability possessed by the movie's actors varied wildly. Bedford could not drive at all and was only ever in the car for close-up type shots, with the production's driving instructor calling the actor's situation "hopeless". Montand and Sabàto faced significant challenges, both of them struggling with even basic skills. Garner, on the other hand, proved competent enough that he trained exclusively with iconic Shelby Cobra driver Bob Bondurant, with the actor's interest in cars growing greatly as a direct result of his involvement in the film. Garner's talents on the road became strong enough that some of the professional drivers, including Bondurant, remarked that the actor could have been a successful Grand Prix driver if he had not gone into making films; in fact, Garner went on to sponsor his own Formula racing team, captured in the 1969 documentary The Racing Scene. His devotion to the part in Grand Prix caused him to do his own stunt in the scene in which a fuel leak in his vehicle sets it on fire. Garner's car was fitted with a higher rollbar and had no seat, since he was too tall to fit in a contemporary F3 car.
The blue and red helmet design that James Garner's character uses is often confused with that of then-Grand Prix race driver Chris Amon from New Zealand; the colours are reversed. Brian Bedford's character’s design was the same as real life 1966 BRM driver Jackie Stewart. As Bedford couldn't drive, this was done so that they could shoot footage of Stewart driving the BRM (with a balaclava over his face to hide that it wasn't Bedford). Sarti's helmet was John Surtees', and Barlini's was Lorenzo Bandini's.
Circuits featured in the film include Circuit de Monaco (Monaco), Clermont-Ferrand (France), Circuit de Spa-Francorchamps (Belgium), Circuit Park Zandvoort (Netherlands), Brands Hatch (United Kingdom), and Autodromo Nazionale Monza (Italy). The Nürburgring (West Germany), Watkins Glen International (USA), and the Autódromo Hermanos Rodríguez (Mexico) were all mentioned in the film but there was no footage shown.
The camera cars used during actual GP races were a Lotus 25 Climax at Monaco and a McLaren M2B Ford at Spa, both driven by 1961 F1 World Champion Phil Hill. A camera was mounted at the front only at Monaco, and an additional one filming the driving wheel was in place at Spa. Aerial shots were filmed from an Alouette III helicopter. These shots were taken so close to the actual roads that the cameraman's shoes became stained with bits of greenery from the tips of nearby trees. Several other camera cars were used during the shooting of staged races, including a modified Ford GT40 and an AC Cobra.
Although making various technological innovations in their filmmaking, numerous difficulties bogged down the movie's production. During filming with wet roads, several cars lost control to the point that one driver broke his shoulder bone and another nearly careened into the upstairs window of a house. The production team often decided to include unplanned accidents caught on film in the final movie, coming back hours later to shoot before-and-after scenes so that things fit in the final cut. For major accidents that were part of the story-line, the crew constructed a special cannon-like device that could fire gutted cars a considerable distance.
Title designer Saul Bass was credited as visual consultant, montages and titles. He made extensive use of multiple split screens. During the making of the film, both Frankenheimer and Garner were interviewed by television personality Alan Whicker for the BBC series Whicker's World.
