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Surprise Performance: Fast Cars With Suspect Horsepower Ratings

Vukasin Herbez June 22, 2020

23. BMW M3 GTR

Every M3 since the mid-80s until today is already a high-strung piece of German engineering ready for racing. However, in the extremely competitive world of motorsports, BMW needed a more efficient weapon. They wanted to go against those Porsches and Ferraris in the IMSA championship of the early 2000s. For that series, BMW prepared the E46 M3. But instead of the high revving 3.2-liter, six-cylinder engine, the M Performance division installed a special 4.4-liter V8. That’s what made the M3 unstoppable at the tracks.

Other teams in the race series cried foul since the V8 wasn’t a production item in the M3 range. As a result, BMW decided to create one of the craziest homologations specials ever made. It was the M3 GTR with 493 HP (600 HP) and full racing equipment and aero package. Interestingly, BMW built 10 cars, but never offered them for sale to the public. Apparently, all 10 are still in BMW ownership, even though there were interested buyers at the high price of $220,000 apiece.

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22. Aston Martin V12 Vantage

Back in the early 2000s, Aston Martin introduced the Vantage, an entry-level model with a V8 engine to compete with Porsche 911. Wearing the signature Aston design, with more than enough power from its 4.3-liter V8, the Vantage proved to be popular. It was high in demand, especially considering that Aston Martin was, and still is, a limited-production manufacturer. The success of the Vantage inspired the Aston Martin engineers to think further. They wondered if they could take the regular V8 Vantage and install the mighty V12 engine from the top-of-the-line DBS model. There was only one way to find out and soon, many prototypes roamed around Aston’s headquarters. They were surprised how good the new car turned out to be.

The V12 engine with 510 HP transformed the nature of this compact sports car and turned it into a British muscle car with fantastic road manners. The real output was closer to 600 HP, which meant that the acceleration was brutal, as well as the top speed. Also, the big V12 didn’t affect the weight distribution or balance. In an era of robotized automatic transmissions, the V12 Vantage was offered with a six and later a seven-speed manual, which understandably proved to be the enthusiast’s choice.

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21. 1967 Chevrolet Corvette L-88 Convertible

The second-generation Chevrolet Corvette, or C2, was available from 1963 to 1967. It was one of the most beautiful and aggressive looking cars from the muscle car era. The C2 caused a sensation when introduced because it was modern-looking, even when the third-generation Corvette replaced it in 1968. The Corvette C2 introduced many important things to the Corvette lineup, such as big block power, independent rear suspension, and disk brakes. It was also a popular and successful racing car in the hands of many teams. Corvette aficionados claim the last year for the C2 was the best because Chevy discretely restyled it with an interesting hood scoop and new engine choices.

Although they introduced the big block 427 Corvette in 1966, it was further refined with four levels of power for the 1967 model year. The list started with a 390 HP, 427 V8 and ended with an extremely rare, valuable, and powerful L-88, 427 V8. Corvettes equipped with this engine were in a class by themselves since the aluminum head L-88 produced close to 600 HP. It also came with a mandatory heavy-duty suspension, brakes, and handling package. Chevy developed this option for racers and it was expensive, almost doubling the price of the basic 1967 Corvette. This made it one of the rarest cars ever, with Chevy building just 17 as a coupe and only three as a convertible. It goes without saying that the L-88-powered 1967 Corvette convertible is expensive and rarely comes up for sale.

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20. 1970 Buick Grand Sport 455

The Buick GS 455 is a special and interesting car in muscle car mythology. As most people know, Buick was a luxury car brand and wasn’t interested in the muscle car hype of the mid-’60s. However, despite its restrained image and older clientele, Buick produced a couple of memorable machines with high horsepower ratings and an unmistakable style. Cars like the Riviera GS, Wildcat, and Skylark GS were true muscle cars that offered uncompromised performance, as well as a high level of luxury and quality.

But in 1970 when GM lifted its ban on engine displacement, Buick decided to introduce one strong model named the Grand Sport 455. This car featured the famous 455 V8 rated at 360 HP (450 hp was the real number), which could launch the big, heavy car to 60 mph in just around 6.5 seconds. This was lightning-fast in 1970 and that speed is still respectable today. Since it was a Buick, they equipped the GS 455 with updated standard equipment and it had a long list of optional extras. Every GS 455 came with heavy-duty suspension, beefed-up steering and brakes, and much more. The price was close to $4,000, a hefty sum for the day, but the GS 455 coupe proved popular with over 8,000 built. They offered GS 455 as a convertible as well and just over 1,000 were built.

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19. 1970 Chevrolet Chevelle SS 454

The Chevrolet Chevelle was always a popular muscle car, combining an affordable price, contemporary design, and a powerful engine. In the 1960s, customers could order the Chevelle with a 396 big-block V8 engine. It was the biggest, most powerful unit rated at 325 or 375 HP, which was more than enough to be a significant player in the muscle car segment. But in 1970, GM’s ban on displacement for intermediate models was lifted, which meant that the Chevelle could get the biggest and the most powerful engine GM had to offer. With its new design, improved mechanics, and one new big-block unit, the Chevelle was set to conquer drag strips in 1970.

The mighty new option was the legendary 454 V8 engine. In standard trim, it was rated at 360 HP, yet that was much lower than the real number. There was an even more powerful version called LS-6. The LS-6 had borderline racing compression of 11.25:1. It used a bigger carburetor and had much stronger engine internals. It was rated at 450 HP but it could produce around 500 HP. Even though the SS option was quite popular in 1970, only around 3,700 cars received the mighty 454 V8 engine. The LS-6 equipped cars were even rarer and Chevy only produced 20 convertibles, making this Chevelle one of the rarest muscle car ragtops in the world.

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18. 1965 Pontiac Catalina 2+2

In the mid-’60s, the Pontiac GTO was the car to have since it was at the forefront of the new muscle car movement. With its performance, powerful engine, and great Pontiac styling, the GTO was the perfect car for the moment. But, it wasn`t the only stellar performance machine coming from Pontiac, and in 1965, there was another pure muscle car icon in form of the Catalina 2+2. Behind this strange name hides a full-size Catalina model, available as a coupe or a convertible, but with a performance twist. The regular Catalina was a handsome, decent selling model, but in 2+2 form, it transformed into a true Gran Turismo with a luxury interior and fire-breathing engine.

Since the Catalina was a full-size model, it was eligible for engines over 400 CID, according to GM rules of the time. The Catalina 2+2 came with the famous 421 V8, and drivers could get the Tri-Power intake system. This power intake system was the same as on the GTO, and it could boost the car’s power to 376 HP (truly over 400 HP) Car buyers could also order limited-slip differentials, heavy-duty steering, brakes, and a whole lot more, making the Catalina 2+2 well-appointed but unfortunately expensive too.

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17. Ford 7-Litre

Since the Mustangs and Thunderbirds were the most famous Fords of the 1960s, the Ford 7-Litre is a forgotten classic luxury muscle car. In fact, most people are not even aware of its existence. Although this is an interesting, powerful car, it had a short history. The story starts in the mid-’60s when Ford introduced a new 7.0-liter engine with 428 CID, which was an evolution of their venerable FE block. They designed the engine to be a powerful street machine with lots of horsepower and torque. At the same time, Chevrolet had the successful Impala SS model with a 427 V8 engine, so Ford needed to compete with it. They envisioned producing their own model as an upscale coupe or convertible with an emphasis on luxury and exclusivity.

So, using a full-size Galaxie two-door hardtop or a convertible platform, Ford introduced a new model for 1966 they called the 7-Litre. The “7” stands for displacement and the “Litre” spelling gave charm to the ordinary Galaxie. But under the hood was a 428 V8 engine with 345 HP (390 hp was the true rating), delivering a convincing performance. Ford put everything they had into this car. In fact, buyers could get A/C and bucket seats standard. They also included a heavy-duty suspension, power everything, special colors, and fancy 7-Litre badges on the sides. However, the 7-Litre was only available for one year. In 1967, the 428 engine was back but just an option on the Galaxie, not a standalone model.

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16. Ford Escort RS Cosworth

The Ford Escort was always an active model when it comes to affordable performance. From the legendary RS 1600 Mk1 to the Escort RS Turbo of the mid-1980s, this was always a competitive-yet-obtainable choice. However, the best Escort RS was the 1992 to 1996 RS Cosworth model. They built it using Sierra RS Cosworth parts. So although the Escort was smaller, it featured the improved 2.0-liter turbocharged engine pumping out 227 HP (about 250 HP was the real output).

The exterior meant business with flared wheel arches and hood cooling vents. Also, it had a massive rear wing that was adjustable. But one of the main features was the rally-proven all-wheel-drive system. In fact, it proved necessary since the car developed over 230 lb-ft of torque. The Escort RS Cosworth was fast for its day. With a 5.8 second 0 to 60 time, it could beat most sports cars of the time period.

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15. Chevrolet Corvette L88

Back in the late ’60s, Chevy wore the crown as the most powerful American carmaker with the advertised power of its 427 V8 engine at 435 HP. All other car brands at the moment had engines with official ratings less than that. But in reality, horsepower wars were raging all over Detroit. When Chevrolet introduced an almost secret L88 option for the Chevrolet Corvette C3 and rated it at the same 435 HP, everybody knew Chevy was lying. The L88 was basically a racing engine for the street. Only the professionals and people close to Chevrolet knew about it, and that’s why they made few L88 Corvettes.

The heart of this package was a steel block and aluminum-head V8 with special internals and intake systems. The output was far more than Chevrolet declared. In fact, it was closer to 550 HP straight from the dealer. In racing tune, the L88 engine could produce up to 700 HP, but it needed special parts and race fuel. One reason Chevrolet lied about HP ratings was to keep it from amateur racers.

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14. Japanese Sports Cars

It became a joke that all Japanese sports cars produced between 1989 and 2005 had horsepower ratings of less than 280 HP. The most common number you will see is 276 HP, but not more than that. Japanese manufacturers had a gentleman’s agreement that the HP ratings of their domestically sold cars would be up to 280 HP and not more. That was for safety, environmental, and insurance reasons. But almost all sports cars they produced in that period delivered much more than just 280 HP. Just think of the mighty Skyline, Honda NSX, Supra Turbo, Subaru Impreza WRX, and all those cars.

They produced over 300 HP, and much more with just a mild tuning job. The Japanese underrating has become famous in the cr industry. Finally, Honda introduced the Legend with 290 HP and all bets were off. The rest of the Japanese car manufacturers followed, and today they have true ratings on their models.

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13. Ford 428 Cobra Jet and Boss 429

Back in the height of the muscle car wars, Ford had two powerful weapons. One was the mighty 428 Cobra Jet and the other was a rare and expensive Boss 429 semi-Hemi engine. Both of those units were true muscle car engines. They had big 7.0-liter V8s with loads of torque and horsepower. However, when Ford decided to rate them at 335 HP, people considered it a joke. In fact, multiple Ford muscle engines like the 427, 429 and even the Lincoln 460 V8 had a rating of 335 HP.

With this HP number, Ford was comfortable with the insurance rates for their customers. Looking at the specifications chart revealed the truth. Despite the fact that all those units produced 335 HP, their torque figures were different, revealing what hid behind the factory ratings. Today, drivers know the famous 428 Cobra Jet from the 1969 Mustang Mach I delivers close to 420 HP, and the crazy Boss 429 semi-Hemi engine makes around 550 HP thanks to its 6,000 rpm redline.

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12. Ferrari F40

Back in the late ’80s, the Ferrari F40 was the ultimate supercar. Not only did it look aggressive and gorgeous, but it was also lightning-fast. Ferrari equipped it with the best high-speed components. Under the slick Kevlar body, there was a full lightweight racing chassis and a compact-but-powerful 2.9-liter twin-turbo V8. The official Ferrari horsepower rating was at 471 HP, a high number for the day. However, some journalists who tested the car objected, complaining that the car made way more than that.

Photo Credit: Evo

Ferrari didn’t address those claims. But recent unofficial testing showed that the car produces between 510 and 530 HP, considerably more than the official ratings. The purpose of hiding that horsepower back in 1988 was to achieve winning numbers in the magazine tests, especially when compared to other similarly-powerful sports cars. Today, the F40 is still fast despite the fact it’s 30 years old. In fact, this car is faster even than the car that replaced it, the F50 featuring a naturally aspirated engine.

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11. BMW M5

Back in the ’80s, the BMW M5 was practically the first sports sedan on the market. This model defined the segment with horsepower that could match most supercars of the era. That’s why the M5 soon became a legendary model and each generation was a big deal in the car world. Fast-forward 30 years, and today there are numerous AMGs, Audis, Jaguars, Lexus, and many more cars that can match BMW performance figures and speed.

A little lying is welcome if it makes the M5 look more capable compared to similar models. The current M5 has a rating of 556 hp for its 4.4-liter twin-turbo V8. This is an impressive number, similar to the power ratings of the closest competitors in its class. However, the performance figures and the subjective feel of the M5 shows the car is significantly stronger and that 556 hp is a conservative figure. A group of enthusiasts took a brand-new M5 to independent testing and came up with results that confirmed the suspicion. The power output was rated at astonishing 620 hp, over 60 hp more than BMW declared. Perhaps BMW wanted to be clear the M5 could win any magazine test and perform better than competitors with the same power.

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10. Buick GSX

The 1970 model year was a watershed year for American muscle and performance models. Never before or since were there so many great models available. Backed by steady sales and great reception of their muscle cars, Buick decided to introduce the ultimate muscle car in the form of the legendary Buick GSX. The GSX stood for Gran Sports Experimental. It was a visually upgraded Gran Sport with a Stage 1 performance package.

The GSX debuted in 1970 with an aggressive graphics package not typical of Buick products. It was available in two bright colors, Saturn Yellow and Apollo White with front and rear spoiler, functioning hood scoops, side stripes, and Rally wheels. The power output was 345 HP from the factory, but everybody knew that Buick engineers hid at least 100 HP and the true performance potential was much bigger. That’s why the GSX was one of the fastest cars of the era.

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9. Porsche 959

Porsche is notorious for fake horsepower ratings. For decades now, the famous German sports car brand has lied about underrating power on their cars. The reason is simple. Just like Ferrari, Porsche is eager to win every magazine test. S they always claim less power so acceleration figures and top speed seem more impressive. It is a cheap trick, but it works. Porsche’s trend of lying started in the mid-’80s with the legendary Porsche 959, the most advanced sports car of its era. Basically, the 959 was a laboratory on wheels and a fast one for that matter.

Porsche installed a twin-turbo engine from Le Mans-winning racecars into the 959 and claimed the car produced 450 HP. The number was impressive for the period and good enough to fight the Ferrari F40. But since the engine was already known, many insiders claimed the 959 produced more than 500 hp. Since the 959 is so rare, we may never know the truth, but racecars with the same engine did deliver over 500 hp. There is reason to believe the legendary 959 is more powerful than the factory said it was.

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8. Pontiac Firebird 400

Sometimes, manufacturers lie not because they want to impress buyers or hide something, but because they need to sell the car. Back in the late ’60s, GM had a rule that forbade manufacturers to produce cars with more than one horsepower for every 10 pounds of a car’s weight. This rule was aimed at stopping manufacturers from producing insanely overpowered models All of GM`s products and brands had to follow this. The only exception was the Corvette. In 1968, Pontiac introduced the new Firebird with the 400 V8 engine, which rated at 320 hp.

Immediately after introduction, car fans were publicly asking the factory why the new 400 V8 engine in the Firebird rated at 320 HP while the same 400 V8 engine in the GTO was 366 hp. Pontiac didn’t reply. Yet soon the answer came from the insiders of the factory. The new Firebird 400 weighed 3,300 pounds. So in order to make it eligible under the GM one hp per 10-pound rule, Pontiac had to rate the 400 V8 engine at 320 hp. Of course, Pontiac knew their fans would see through this stunt, but they needed to do it in order to sell the new model to the general public.

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7. Dodge Neon SRT 4

In SRT 4 form, the otherwise ordinary Dodge Neon was a true performance car with great potential and a cool secret. Since the Neon was conceived as an economy compact to battle Japanese and Korean cars, it was equipped with low-powered four-cylinder engines and dull drivetrain options. But Dodge wanted to make it a competitor in the hot hatch class, and that meant the Neon needed more power under the hood and a new name. The SRT 4 means “Street Racing Technology” and the number four designates the number of cylinders. Under the hood was a 2.4-liter four with a turbocharger. At first, it had 215 HP and the number later rose to 230 hp. With this powerplant, the Neon SRT 4 was a fast and nimble car that soon earned respect on the street. Photo Credit: Dodge Forum

Street racers found out the Neon’s engine was easy to tune to achieve high horsepower ratings. Jumping from the stock 230 hp up to 330 hp was just too easy. Soon, rumors started that the stock SRT 4 engine was much powerful than the factory stated because drivers could easily pass the 300 hp mark if they put on just a few bolt-on accessories and did a mild tune-up job. The factory didn’t issue any statements until the Edmunds.com test team took one stock Neon SRT 4 and tested it. The result was an impressive 285 hp from the factory. No wonder the Neon had such a good performance and was the favorite with the street racing crowd.

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6. Ford GT

The story of the gorgeous Ford GT starts in the mid-’60s when they introduced the GT40, a racecar created with the sole purpose to beat Ferrari on the race track and in the legendary 24 Hours of Le Mans race. The beautiful racer did just that four times in a row, shaming Italian racecars and stopping their winning streak. The original GT40 was called that because it was only 40 inches high. Almost 40 years after the release of the original car, Ford returned with the GT, a modern take on the classic form. In contrast to the original car, which was a pure racing machine, the modern-day Ford GT was a sports car with no racing intentions. Produced between 2005 and 2006, the Ford GT featured retro-futuristic styling and the same proportions as the original car.

However, behind the driver wasn’t a big block 7.0-liter engine but a modern, 5.4-liter supercharged V8. This unit delivered 550 hp, which was more than enough to attract the attention of sports car fans and become one of the most powerful cars of the day. But today there is actual proof that Ford was shy about the power figures and that the GT produced significantly more than they stated. Since the production of the Ford GT was big at around 4,000 models, some owners measured the car’s output. The results were astonishing and a perfectly stock GT delivered over 620 hp. Since it had a supercharged engine, various states of tune and different fuels could produce even more power.

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5. Hemi 426

From 1966 to 1971, the Chrysler Corporation produced the infamous Hemi 426 engine, the definitive muscle car engine of all time. It was the top-of-the-line engine option for select Dodge and Plymouth muscle cars. It was the most expensive and also the most powerful. The name, “Hemi,” comes from hemispherical combustion chambers inside the heads of the engine and “426” is its displacement measured in cubic inches. This engine was officially rated at 425 hp throughout its lifespan, but everybody knew this number was a joke. The Hemi technology allowed this engine to achieve a much higher rpm range than the standard big-block V8 engine of the day, and that meant more horsepower and torque.

Big valves allowed much better airflow, which also helped the power. Straight from the box, the Hemi 426 could produce around 500 hp without any problem. Most owners decided to do some modifications like new carburetor jets to easily get 550 hp without much work. That’s more than 100 hp above the factory specifications. Horsepower has always been a way to distinguish fast cars from slow ones, but the statistics have not always been real. Although the car makers have their reasons, it’s easy to test them to find out the actual horsepower. Thankfully, today’s carmakers are more truthful about horsepower.

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4. Ford Mustang Boss 302

The third redesign of the Mustang appeared for the 1969 model year, and the car grew again. Ford produced it for only two years in 1969 and 1970. The Boss 302 featured a 302 V8 engine conservatively rated at 290 HP. The real output was closer to the 350 HP mark though.

The Boss 302 was a model Ford intended for racing in the Trans-Am championship. Apart from the blackout hood, spoiler on the trunk, and other details, it featured a stiff, track-tuned suspension, a close-ratio gearbox, and a high revving engine. The car was light and without any unnecessary luxuries, so the performance was impressive.

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3. Pontiac 400 Ram Air IV

Back in the late ’60s, Pontiac’s Ram Air engines were one of the hottest mills in the muscle car class. This engine featured a four-barrel carburetor with the famous Ram Air induction system. The ratings were 360 HP in its RA III form. They installed those engines in GTOs, making them the perfect street racers of the era. However, in 1969, Pontiac presented the Ram Air IV version of the same engine with the same advertised horsepower rating of 360 HP. The two engines looked the same, but the RA IV had much different internals underneath.

It had different engine heads, camshafts, and valves. It also had more compression and a higher rev limit. The Ram Air IV was capable of much more than 400 HP. However, the factory decided to rate it at 360 HP for insurance reasons. Unfortunately, the Ram Air IV was an expensive option so Pontiac didn’t make many of them.

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2. Ford Mustang SVT Cobra

Inspired by the wild SVT Cobra R’s from the ’90s, they didn’t name the 2003 model “R” since it wasn’t limited in production. Ford made it available to the public rather than just racing drivers and private teams. However, this SVT Cobra was an interesting, important model for the Mustang dynasty since it featured two firsts. It was the first factory supercharged engine with an independent rear suspension. For the SVT, Ford took the standard 4.6-liter block and mounted different heads and a supercharger to get 390 HP and 390 lb-ft of torque.

They named the engine the “Terminator.” The rumor was that it delivered more than the advertised 390 HP. In fact, it was much closer to 430 HP. To handle all that power and torque, Ford equipped the SVT Cobra with an independent rear suspension setup like the first Ford GT. This helped stability at high speeds and hard launches, making this Mustang handle like a dream.

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1. Buick GNX

The ’80s were the dark ages of muscle cars and American performance, but there were a few bright moments. One of the cars that restored faith in muscle car movement in the ’80s was the mighty Buick GNX. The story of this model is an interesting one. Back in 1982, Buick started experimenting with turbocharging its line of standard V6 engines. The results were satisfying, so engineers got permission to develop a performance version with better acceleration figures. Soon there was a Buick Grand National with 175 HP, which wasn’t impressive but was a start.

In the next couple of years, the Grand National got a bigger engine and more power, jumping from 175 HP to 200 HP and finally to 235 HP. With those numbers came the acceleration times of under six seconds. Those black Grand Nationals were quick cars. But in 1987 came the ultimate version Buick called the Grand National Experimental, or GNX for short. It featured the same 3.8-liter turbocharged V6 but with 275 HP and 0 to 60 mph times of 4.7 seconds. Lots of car enthusiasts claimed the GNX produced at least 300 HP since it was extremely fast. At that moment, Buick GNX was the fastest accelerating production model in the world. At $29,000 it wasn’t a bargain, but there is a widespread legend about owners who paid the lease on these cars by street racing them for money.

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Surprise Performance: Fast Cars With Suspect Horsepower Ratings

23. BMW M3 GTR

22. Aston Martin V12 Vantage

21. 1967 Chevrolet Corvette L-88 Convertible

20. 1970 Buick Grand Sport 455

19. 1970 Chevrolet Chevelle SS 454

18. 1965 Pontiac Catalina 2+2

17. Ford 7-Litre

16. Ford Escort RS Cosworth

15. Chevrolet Corvette L88

14. Japanese Sports Cars

13. Ford 428 Cobra Jet and Boss 429

12. Ferrari F40

11. BMW M5

10. Buick GSX

9. Porsche 959

8. Pontiac Firebird 400

7. Dodge Neon SRT 4

6. Ford GT

5. Hemi 426

4. Ford Mustang Boss 302

3. Pontiac 400 Ram Air IV

2. Ford Mustang SVT Cobra

1. Buick GNX

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