10 Surprising Facts About American Muscle Cars

The first two years of Carroll Shelby's Mustangs are the most desirable to many Mustang purists. Those 1965 and 1966 GT 350s were light, simply styled, and perfect for track work. But the later 1967 and 1968 cars offered more fun under the hood and were the machines of choice if you wanted to win drag races.

For the first time, '67 to '68 GT 500 Shelbys came with 355-hp 428-cubic-inch big-block power under the hood. Car testers of the day saw quarter-mile time slips in the mid-to-low 14-second bracket—quick for the day. The Shelby Mustangs received more scoops and flashier styling than the older cars to match the new-found power and torque. And the even quicker KR (King of the Road) high-performance model was available in 1968 too.

Little-Known Fact: The 1967 Shelby Mustangs used Mercury Cougar tail lamps, but the 1968 models used lamps from the '66 Ford Thunderbird.

The third generation of America's sports car, the Corvette, had an incredibly long run: 1968 to 1982. So when it came time for GM to launch the next-generation C4 Corvette, there was wild speculation about the car. Some predicted it would use a midengine chassis, like an Italian exotic. And others thought it might use a rotary engine, like Mazda's.

In the end, the next Vette wasn't radical. It still had a small-block Chevy V-8 up front driving the rear wheels. That first year, it cranked out a meager 205 hp. But after a switch to a new, tuned port fuel-injection system in later years, horsepower jumped—and so did performance. Five years later, Chevy debuted the first ultra-performance Vette since the 1960s: the 375-hp ZR-1.

Little-Known Fact: There is no production 1983 Corvette. Although 1982 was the last year for the third-generation Corvette, Chevy decided to wait until the 1984 model year to launch the all-new car. Why? Some sources claim tighter emissions regulations necessitated more time for development. Others say that quality glitches at the factory were the real reason. All we know is every 1983 Corvette prototype was destroyed, except one: a white car that now lives at the National Corvette Museum in Bowling Green, Ky.

The 1969 Dodge Daytona and its sibling, the 1970 Plymouth Superbird, are arguably the most radical vehicles to emerge from the muscle car wars. But the Daytona, as the name might suggest, wasn't designed for street racing. It was built to win Nascar races on the superspeedways—the longest and fastest tracks.

To increase top speed, engineers took the Charger to the wind tunnel. The aerodynamic modifications to the big Dodge included a nearly 2-foot-tall rear wing, a flush rear window, and a longer, sloped nose cone. The results were impressive. The race version of the Daytona became the first car in Nascar history to break 200 mph. After numerous Dodge wins in 1969 and some by Plymouth in 1970, Nascar's new rule book banned these cars. The production cars, which came packing a 440 big-block or the legendary 426 Hemi, are sought-after collector cars today that bring more than $150,000 at auctions.

Little-Known Fact: The Daytona's aerodynamic modifications over a those of a standard Charger helped lower the coefficient of drag to 0.28—an excellent figure even by today's standards. But did that huge rear wing really need to be so tall to maximize rear-end downforce? According to legend, no. The reason for the exaggerated height of the wing was so that the trunklid on the production cars could pass underneath it and fully open.

The 442 (which gets its name from its four-barrel carburetor, four-speed manual, and dual exhausts) was based on the Cutlass and become the hot muscle machine for the Oldsmobile division. It shared its platform with two other hot GM machines, the Chevy Chevelle SS and the Pontiac GTO. And like the GTO, the 442 was only a trim level at the beginning. But by 1970, you could get a huge 455-cubic-inch big-block V-8. And when equipped with the even more potent W30 parts, the motor made 360 hp and a whopping 500 lb-ft of torque. It could hit 60 mph in less than 6 seconds, which was very quick for the time—especially for an Olds.

Little-Known Fact: Actor James Garner raced a beefed-up 1970 Olds 442 in the NORRA Mexico 1000 (a precursor to the Baja 1000), where it won second in class. The Goodyear Grabber, as it was known, was built by legendary Baja-race-vehicle guru Vic Hickey and sponsored by Goodyear tires. The vehicle was recently restored and put up for sale.

By the late 1970s, muscle car performance was a mere shadow of what it had been years earlier. The latest emissions controls, combined with high gas prices and stratospheric insurance costs, caused most automakers to severely dial back horsepower.

But not Pontiac. The Trans-Am had been riding a new wave of popularity since its starring role in the movie Smokey and the Bandit. For the 1978 model year, Pontiac added to the excitement by actually increasing the horsepower of its top-level Trans Am from 200 to 220. The brand also developed a special handling package called the WS6 that added a sport-tuned suspension, wider 8-inch wheels, new tires, and quicker steering. The result was a Pontiac Trans-Am that was actually quicker and handled better around a track than the Chevy Corvette.

Little-Known Fact: The Pontiac's T-top roof, which first became an option in 1976, was as close as a buyer could get to a convertible Trans Am. These lift-out roof sections were initially made by Hurst and were known as the Hurst Hatch. The problem was, they leaked. This led Pontiac to develop its own T-tops within GM's Fisher body division and launch the option midway through the 1978 model year. So some '78 Firebirds have Hurst T-tops and others have the Fisher units. You can spot the difference because the Fisher glass roof panels are larger than the Hurst Hatch ones.

In the late 1960s and early 1970s, Nascar was in its golden age. Automakers took the business of stock-car racing seriously and would dream up engines and bodywork for racing that were often too wild for the street. All the automakers needed to do was sell 500 of these radical cars and they could run them in Nascar.

The Boss 429 Mustang was just such a beast. Although the Mustang didn't compete in Nascar, the 375-hp 429-cubic-inch V-8 under its hood was designed specifically for racing and built to rev to 6000 rpm. The problem was, this motor did not perform well on the street. It was slower than the other big-block Mustangs at the time. The Nascar-bound V-8 was monstrously large and did not fit in a stock Mustang's engine bay. So Ford contracted Kar Kraft in Brighten, Mich., to handle the job. The company relocated the shock towers, widened the track of the front end using unique componentry, relocated the battery to the trunk, and fitted a smaller brake booster—all to make room for this beastly powerplant to fit in the Mustang. Today, the rarity and mystique behind the Boss 429 has pushed values at auction well beyond $200,000.

Little-Known Fact: There were actually three different 429 engines installed in the Boss 429 between '69 and '70. The hardcore "S-Code" was installed in early cars and filled with race-duty parts. But the S-Code had warranty problems, reportedly because of an incorrect assembly process. So the "T-Code" with lighter-duty parts was used in some cars. The later "A-Code" version of the 429, equipped with smog equipment and a new valvetrain, appeared toward the end of production.

When GM relaxed its longstanding rule forbidding engines larger than 400 cubic inches to be installed in midsize cars, it set off a muscle frenzy across the company's divisions. Oldsmobile put the huge 455-cubic-inch into its 442, and Chevy installed a unique 454-cubic-inch V-8, the LS6, into its Chevelle SS.

A conservative estimate of the LS6's power puts it at 450 hp and 500 lb-ft of torque. But thanks to its high 11.25:1 compression ratio and giant Holley 780 CFM carb, the LS6's real output in the Chevelle SS was closer to 500 hp, many experts claim. Our pals at Car and Driver tested one in 1970 and found it hit 60 mph in just 5.4 seconds, running through the quarter-mile in 13.8 seconds. And that was with the skinny low-grip tires of the day; that same car with modern rubber would be much quicker. The LS6 carries the highest factory horsepower rating of all muscle cars.

Little-Known Fact: The Chevrolet Corvette has always been Chevy's top performance car. And up until the LS6, GM wouldn't allow any other Chevy to carry a horsepower rating higher than that of the Corvette. But somehow that stance was relaxed for 1970—the highest horsepower engine you could get in a 1970 Corvette was a 390-hp LS5 454. An LS7 was planned with 465 hp, but it was never officially sold. So why no LS6? An LS6 Corvette was offered for 1971, but its potency slipped (at least officially) to 425 hp.

Pontiac owned the muscle scene in the early 1960s. In fact, the 1964 Pontiac GTO is widely regarded as the very first of the breed. But by 1968, that car had plenty of competition. The thought within Pontiac was to make a cheaper version of the GTO with a smaller 350-cubic-inch engine called the ET (for "elapsed time") a drag-racing term.

Pontiac boss John DeLorean didn't like that idea. To him, no GTO ould have an engine that small. Instead, the team built a car one step up from the regular GTO. DeLorean himself named the car after a popular skit on the TV show Rowan and Martin's Laugh-In. The Judge featured the 360-hp Ram Air III engine standard, but buyers could also opt for the more hardcore 370-hp Ram Air IV. The rarest of all were the GTO Judge Ram Air IV convertibles—only five were built in 1969.

Little-Known Fact: The original TV commercial for the Judge featured the rock band Paul Revere and the Raiders singing about the GTO out on a dry lakebed. According to the book Pontiac Pizazz, by Jim Wangers and Art Fitzpatrick, the lead singer, Mark Lindsay, was a car guy and loved the Judge, so he wrote a song about it. Wangers claims this commercial is considered one of the earliest rock-music videos.

Chevrolet's Central Office Production Order (COPO) system was designed for fleet sales; it was intended to spec out heavy-duty suspensions for cop cars and stain-proof interiors for taxicabs. But enterprising dealers with the right connections, such as Yenko Chevrolet in Pennsylvania, figured out that Camaros could be ordered this way, too. And given the right order codes, the dealer could spec out a fire-breathing monster of a Camaro that Chevy didn't really want you to own.

The production order 9561 specified a 427 big-block V-8 rated at 425 hp—just like a Vette. But the even rarer COPO 9560 called for an all-aluminum ZL-1 427 V-8. Though this engine was rated with just 5 more hp, it was widely known that this race-spec engine delivered more like 550 hp. Only 69 ZL-1 Camaros were built, and these cars command prices in the $400,000 range at an auction

Little-Known Fact: The aluminum ZL-1 427 V-8 in the 9560 COPO Camaro is essentially a race engine. Chevy originally developed this 427 motor for the Chaparral racing team to use in the Can Am series. There are no external emblems on a ZL-1 Camaro that let you know what's under the hood—only plain-vanilla Camaro badges.

Long after the big block V-8-powered muscle cars of the 1960s and 1970s went, Buick brought back some of that magic in the 1980s. The Buick GNX, based on the Grand National (which is itself a hot-rod version of the Regal coupe), was equipped with a potent, turbocharged V-6. The GNX package brought the Grand National's horsepower from 245 up to 276. Car and Driver tested one in 1987 and recorded a 0-to-60-mph time of just 4.6 seconds, making it one of the quickest cars on the market. Buick made only 547 of these black beasts. Many were squirreled away into storage as investments.

Little-Known Fact: Buick had quite a few of these engines left over when it stopped production of the GNX—so Pontiac picked up the turbo V-6s and put them in the 1989 20th Anniversary Trans Am. It was conservatively rated at just 250 hp, but true GM enthusiasts knew the potential that lay under the hood of that Trans Am.