Donald Koleman, president of New Hampshire-based Competition Motors, towers above the robin’s-egg blue Bugatti Type 51 Grand Prix racecar parked on the showroom floor. With its horseshoe-shape radiator, excessively louvered hood, spindly axles, and polished aluminum wheels, this diminutive, open-cockpit rocket won 10 races between 1932 and 1937, while setting nine international records for speed and endurance. “It’s the single-most successful Bugatti in history, worth—I don’t know—$5 [million] to $7 million,” says Koleman, a former attorney who gave up litigation to rebuild and sell vintage sports cars. It’s for sale, too. “I don’t expect it to be driven,” he adds. “It’s just too valuable.”

But hey, you never know. A growing number of private collectors—investment-portfolio manager Jim Glickenhaus (among his holdings: a 1967 Ferrari 330 P3/4); former Microsoft president Jon Shirley (who occasionally takes his 1932 Alfa Romeo 8C for a spin around the racetrack); and Rob Walton of Wal-Mart fame (he just drove his 1965 Cobra Daytona to victory in Monterey, California), to name a few—like to cruise the city streets in their museum-quality vintage coupes. Some even drive their cars to the track, then race the hell out of them.

“The dollar value of these cars can be astronomical,” says Casey Annis, editor and publisher of Vintage Racecar Journal. One Japanese investor paid $15 million for a 1962 Ferrari 250 GTO, and buyers have shelled out as much as $10 million for prewar racers built by Auto Union (the precursor to Audi), Alpha Romeo, and Mercedes Benz. Even the most expensive new models top out at less than $2 million.

States allow classic racecars to hit public highways carrying whatever safety gear they rolled off the factory floor with. If it came without seat belts or turn signals—which is common, especially in prewar racers—no big deal. But rocketing around a track is an entirely different matter. When Ed Archer, of Archer and Associates in Hayward, California, a firm that appraises classic vehicles, wants to race his open-wheel 1915 Model T Ford (which he himself valued at between $30,000 and $50,000), he must have a seat belt, a side-view mirror, and a fire extinguisher. The car didn’t need any safety gear when it was racing on dirt and wooden tracks more than 90 years ago. Racing regulations also require him to wear current fireproof gear—a suit, a helmet, and gloves—a far cry from the goggles and white coveralls favored by the original driver.

“Owners don’t want to do anything stupid,” says Archer, justifying safety equipment, which is often cleverly concealed. He’s driven the ancient Ford from California to Indianapolis, cruising down the highway at 70 miles per hour, and then slapped on the protective gear and raced it around the Indy 500 track. “In a historic racecar if you do something stupid, you may not come out if it.”