Modern Living: Muscle with Hustle

In last week's twelve-hour endurance race at Sebring, Fla., the one-two finish of the fast new Porsche prototypes was almost a foregone conclusion. But the performance of ex-Road Racing Champion Roger Penske's Chevrolet Camaros, which placed third and fourth, was a startling surprise. The Camaro, after all, is a standard road car, not a finely tuned racer. Penske's entries were no run-of-the-showroom models, to be sure; at a cost approaching $25,000 apiece, each machine had been modified for racing with the addition of everything from a souped-up 440-h.p. engine to disk brakes on all four wheels. Yet the cars merely mirrored, albeit on a grand scale, a burgeoning off-track trend toward faster road cars—and Ralph Nader be damned.

To tap the growing market for high-performance "street iron," triggered by the introduction of the Ford Mustang in 1964, Detroit is offering an increasingly wide array of hot intermediate-sized "muscle" cars, and an even wider range of optional extras designed to make them hotter still. At the International Auto Show in Manhattan last week, the muscle cars were there in force, from Plymouth's Road Runner to Pontiac's Firebird, and they made an obvious hit with visitors. Says Ray Brock, publisher of Hot Rod magazine: "The high-performance buff can now literally 'build' his own individualized machine right on the showroom floor." Among the fastest of the new hybrids:

>Plymouth's Road Runner, a stripped-down version of the Satellite, which, with the addition of the dome-shaped 426-cu.-in. "Hemi" engine,* covers the quarter mile in a blistering 13.5 sec. from a standing start, hits a top speed of 107 m.p.h. "Beep-beep" goes the horn, duplicating the sound made by the cartoon character, as a warning to slowpokes that the Road Runner is on its way. Cost: $3,610.

> Ford's Carroll Shelby Cobra GT-500, a modified Mustang with heavy-duty suspension and transmission, hood scoops that ram extra air directly into the carburetors, and a new 428-cu.-in. engine that will be available next month on Ford's Mustang, Torino and Cyclone and Mercury's Cougar as well. Padded roll bars and shoulder harnesses are standard on the Shelby Cobra, as well they might be: the $4,200 car winds up to 150 m.p.h.

>American Motors' AMX, a $3,245 sports coupe on the market for less than a month. A 290-cu.-in. engine is standard, but another $123 rates a 390-cu.-in. replacement. Testing an extra-powered AMX, Land Speed Record Holder Craig Breedlove got the car up to 170 m.p.h.