San Francisco

At the very top of Taylor and Vallejo streets here on Sunday morning, I stopped to take in the view. Idling in a 2011 Ford Mustang V6, I looked down through the windshield at the impossibly steep hill below, immortalized in the 1968 film "Bullitt" starring Steve McQueen.

Seated next to me was Loren Janes, 79, McQueen's longtime stunt double and the last surviving member of the "Bullitt" car crew. Mr. Janes drove the green Mustang in the movie's most daring and riveting scenes—the one down Taylor Street and the other along Guadalupe Canyon Parkway. I even brought along a CD of the "Bullitt" soundtrack for the ride.

Two weeks after the death of "Bullitt" director Peter Yates, Mr. Janes and I set out to honor him by driving the movie's chase route—cautiously. "Peter wanted everything about the chase to feel risky and rough," said Mr. Janes, whose stuntman credits include more than 500 movies and 2,100 TV episodes. "Peter never got cold feet about any of the stunts that coordinator Carey Loftin lined up. He knew that a memorable film needed to be on the edge."

"Bullitt" still ranks high among car-chase enthusiasts. Several websites are devoted to information and trivia about the 10-minute chase sequence. Others have posted "then and now" images of chase locations. In fact, fans can even retrace the routes thanks to an online Google map that a fellow afficionado has marked up.

On YouTube, the "Bullitt" chase remains chilling. The green Mustang and black Dodge Charger tear through urban residential neighborhoods, bouncing off hills like Hot Wheels cars and banging into each other along the way. Yates raised the stakes even further by placing cameras in the cars, creating a new genre in which the viewer becomes a queasy passenger.

As Mr. Janes and I drove around the city, three myths were shattered. First, despite the hype, McQueen did not do his own driving in the movie's most dangerous scenes. "Steve was a great driver, but he was only behind the wheel for about 10% of what you see on screen," said Mr. Janes, who was McQueen's stunt double from 1959 to 1980. "He drove in scenes that required closeups—but not in the ones that could kill him. Steve always asked me first whether a stunt was too dangerous for him to take on."

How well would you handle the streets of San Francisco? Warner Bros. / The Kobal Collection

The second revelation was that Mr. Janes was the stuntman who hurtled down Taylor Street in the Mustang and repeatedly sideswiped the Charger on the Guadalupe Canyon Parkway at 90 miles per hour. For years, Bud Ekins was assumed to have been that driver. "I was working on another film at the time, so Bud drove the early scenes before I arrived on the set," Mr. Janes said. "Many assumed he had driven them all, which wasn't the case."

And the third revelation? The chase's most breathtaking driving scenes are terrifying in real life, even for someone who grew up in 1970s muscle cars. As we began to descend Taylor Street's first sheer hill, Mr. Janes offered a warning: "Don't even try going down here the way I did. Our cars were heavily modified with racing shocks, special overinflated tires and skid bars on the underside. A factory car would come apart on impact if you sent it into the air here."

Point well taken. The pitched angle and approaching stop sign at Green Street forced me to inch down the hill's first leg at 15 mph. In the film, Mr. Janes hurtled down these hills at 60 mph in pursuit of the Charger, using each level intersection as an asphalt ski jump. "Traffic was cleared for us then," Mr. Janes noted. "We didn't have to worry about trucks and pedestrians—the way you do."

Fine, but how did he send the Mustang into the air? "I gunned the engine just as the back wheels leveled off at the cross streets," Mr. Janes said, not noticing that I had rolled gingerly through the stop sign to gain momentum.

As my rear wheels leveled off at the intersection, I hit the gas moderately. The Mustang surged forward, and I could feel the car trying to take flight where the flat surface ended abruptly and the hill resumed. "Feel it?" Mr. Janes asked coolly. "Any faster, though, and this car will take off, leaving the underside damaged when we come down."

At Union Street, the next intersection, I gunned the engine lightly again. This time the Mustang lifted a little more and settled back down harder. I asked Mr. Janes how he managed to avoid being tossed around in the cockpit like a marble. "When I left the hill, I pushed back into my seat using the wheel. That held me stable," he said.

In the movie, the Taylor Street sequence ends with the Charger hooking a hard left on Filbert Street and the Mustang following. As we near Filbert, I asked Mr. Janes how he made the turn while traveling so fast. "I started turning the wheel about three-quarters of the way down and fishtailed off to the right," he said. "Otherwise I would have overshot the turn or flipped."

Born in Sierra Madre, Calif,, Mr. Janes was a high-school calculus teacher when he was discovered by one of his students, whose father worked at MGM. The student knew Mr. Janes was a gymnast, former Marine and skilled swimmer. He suggested that Mr. Janes offer his skills for a 90-foot stunt dive off a cliff on Catalina Island for an Esther Williams film. Mr. Janes's stunt career was launched with that perfect dive in 1954.

In 1959, Mr. Janes met McQueen on the set of TV's "Wanted Dead or Alive." His first stunt as the actor's double required him to dive through a barn window, roll to his feet, vault over two horses, land on McQueen's animal and ride off. "It went flawlessly," Mr. Janes said. "From then on, Steve wanted me on all of his pictures."

After driving down Taylor Street, Mr. Janes and I toured the other chase locations. In the Mission section, we re-created McQueen's U-turn and zoom up York Street. Next came Potrero Hill, where the two cars tear down Kansas Street starting at 20th Street. I peeled out there.

We even drove out to Guadalupe Canyon Parkway, about 20 minutes from San Francisco. In the movie, Mr. Janes sideswiped the side of the Charger multiple times in an attempt to drive it off the road. "Bill Hickman, the great stuntman, drove the Charger," he said. "Bill and I spent a long time working out those bangs in advance."

When the filming of "Bullitt" ended, McQueen offered Mr. Janes one of the three tricked-out Mustangs used in the film. Mr. Janes passed, fearful he would always want to drive it too fast. "Besides, I already had this," he said, removing a 1964 Rolex Submariner from his wrist. On the back was an inscription: "To the best damn stuntman in the world. Steve."

Mr. Myers writes about jazz, film and the 1960s at JazzWax.com.