I too went to see Grand Prix in 1966 but missed most except the opening scene as I spent the time necking. I didn't see the full movie til later and I own a copy now.

The fellow who played Clark (sort of) couldn't drive a stick so they had him wear a scarf over his mouth because all the shots of the full car with him in it were played by other drivers. They used formula three cars (similar to my Formula Ford) with dummy pipes to look like the real cars for shots with the actors driving. A lot of real drivers were in the movie, at least a dozen including Gurny, G Hill, P Hill, and many others.

I often get it out or LeMans if I feel I need some motivation before an autocross event.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.