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Mystery Muscle: These Strange GM Muscle Cars Will Blow Your Mind

Vukasin Herbez April 10, 2023

Oldsmobile Jetfire

The Jetfire is a very important model for automotive history that unfortunately never got the respect it deserved. It was the first turbocharged passenger car along with the Chevrolet Corvair Monza. However, Oldsmobile’s system was far more complex and powerful than Chevrolet’s. For that reason, it deserves a detailed look. Engineers took the compact F-85 model and retained its small 215 cid V8 engine, which developed 185 HP and gave it a new forced induction intake system. It included a Garett turbocharger and a special “Turbo Rocket Fuel” tank, consisting of distilled water, methanol, and a corrosion inhibitor mixture injected into fuel and air mixture to prevent the detonation (via Car Throttle).

The new V8 delivered 215 HP, translating to one HP per cubic inch, making it one of the top performance cars of the day. It was almost as fast as the Corvette with a 0 to 60 mph time of around eight seconds. However, the Jetfire had problems from the beginning. Many of the issues were owner-related. Very soon, Jetfire got a bad reputation despite the praise from automotive magazines. After just two years and around 10,000 examples, Oldsmobile decided to kill the car and turbocharging technology. The Jetfire was soon forgotten and just a few enthusiasts now remember these Oldsmobiles.

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Chevrolet Impala Z 11

In 1963, Chevrolet introduced the limited but highly influential Z-11 option on the two-door Impala. The idea behind the Z-11 was to present the best street/strip technology in one model. And the first order was to shed some weight by using aluminum panels, grilles, hoods, and fenders (via Auto Evolution).

The radio and heater were gone, and they stripped the interior of all unnecessary luxuries. Chevrolet built only 50 to 57 Impala Z-11s in 1963, and single-digit models are known to survive today. They kept the package secret, so the public didn’t know the available model.

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1963 Corvette Grand Sport

In the early ’60s, the Corvette had already proven itself on the market, and now it was time to establish itself on the race track. Back in the day, Shelby Cobra by Ford was dominant on the tracks and the Corvette team wanted to beat it. So, Zora and his team prepared 5 Grand Sport Corvettes with modified bodies, special suspension, fully-loaded race engines, and a host of other specially built components (via Motor Trend).

Grand Sport Roadster Via Motor Week — Photo Credit: Pinterest

The Grand Sport Corvette had over 550 HP and was capable of brutal performance. The Corvette team had big plans and entered the Grand Sport Corvettes in several races with mixed success when the decision from the top of General Motors stopped all racing activities. For some reason, GM stopped investing in all forms of racing in early 1963. This killed the fantastic Grand Sport program before it could prove its worth, making the Corvette Grand Sport one of the greatest “what if” stories of the racing world. All five cars survived and are accounted for.

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Chevrolet Chevelle Z16

Most car fans know a lot about the Chevelle. For decades, it was Chevy’s primary mid-size offering they produced in the millions. It was available in many markets, not just domestic ones. However, only a few know about the Chevelle Z16. It was a high-performance model Chevy produced for one year only in just 200 examples (via Hemmings).

Today, it’s an extremely rare and valuable piece of Chevrolet’s history. So, what exactly is the Chevelle Z16? It’s a fully-loaded regular Chevelle with several other speed-boosting upgrades. They include a 396 V8 engine with a Muncie four-speed gearbox. It also has a heavy-duty suspension and updated equipment. Even some dealers weren’t aware this option existed because Chevrolet refused to market the Z16, making this Chevelle a secret model. The Z16 was fast and expensive for a Chevrolet, probably why they made only 200 of them.

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Oldsmobile Toronado GT

The Toronado GT was a special package for Oldsmobile’s personal luxury cruiser. The car was available for a few short years ending in 1970. From the outside, the Toronado GT looked like an ordinary Oldsmobile, and the same 455 engine powered it, but the difference was the details (via Hemmings).

The GT package upped the power to a magical 400 HP, added various suspension upgrades, bigger and stronger front disc brakes, and better interior equipment. The GT was a rare option, and people seldom decided to order Oldsmobiles with this package. That is precisely why nobody knows about it today.

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Chevrolet Chevelle “Heavy Chevy”

In 1971, dark clouds were on the horizon for muscle car enthusiasts. Tightening government regulations, high insurance rates, and environmental standards limited the segment significantly. Manufacturers understood they had to act fast to save the market. So the first thing they did was to introduce economy versions of their popular muscle cars (via Hemmings).

They gave their cars smaller engines but interesting designs to maintain their appearance and popularity. One of those models is the 1971 Chevelle “Heavy Chevy.” They positioned it as an interesting one-year-only muscle car below the Chevelle SS lineup. The Heavy Chevy came with a 200 HP 307 CID V8 engine, but you could opt for a 245 HP 350 CID V8 engine. The most powerful version was the 300 HP 402 CID V8. But if you wanted the top-of-line 454 big-block V8, you had to go the SS route. The “Heavy Chevy” was a popular model. They built over 6,500 in a year, and it’s very rare and obscure today.

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Chevrolet Laguna 454

Even though it was the upscale model of the early ’70s Chevelle lineup, people overlooked the Laguna. Today, they’ve forgotten it. Back in the day, Chevrolet tried to make the Laguna desirable by giving it several body styles. It also had the 350 V8 as the base engine, although with only 145 HP, and many options (via GM Authority).

But nothing helped, so after a few years, they discontinued the Laguna. The particularly interesting thing is that the Laguna is one of the last classic Chevrolet muscle cars. This was because they offered it in a coupe body style for 1974 with an optional 454 V8. Although the power level wasn’t high, the big 454 still produced enough torque to spin the rear wheels.

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Chevrolet Monza Mirage

The Monza debuted in 1975 as the newest GM compact model with a modern design, sound equipment, and a wide arrange of versions and trim levels. It succeeded the Chevrolet Vega and sold well on the US market and abroad. However, the lack of performance version was evident since the compact and relatively light platform would benefit from a powerful engine. Chevrolet didn’t think the performance model or a muscle car version would have a big market, so it didn’t bother developing it (via Truth About Cars).

However, Chevy contracted an outside company, Michigan Auto Techniques, to make the Monza a GM muscle car in 1977. Called the Monza Mirage, this one-year model was made in 4000 examples and featured a 305 V8 with only 145 HP. The design was quite striking with a white body, front and rear spoilers, and special wheels. The paint scheme was patriotic, with red, white, and blue stripes all over the body. Chevrolet realized there was still a market for sporty variants and decided to introduce the Monza Spyder in 1978. Michigan Auto Techniques was without a contract for 1978, sending the Monza Mirage into the history books.

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Photo Credit: Mecum

Chevrolet Vega Cosworth

After the debacle of the Chevrolet Corvair in the ’60s, the company was reluctant to enter the compact market again. Since the segment grew, Chevy didn’t have a choice. So, a new Chevrolet Vega was introduced as a 1971 model. The Vega was a compact, modernly-styled model with three basic body styles. There was a two-door coupe, two-door sedan, and a more practical three-door wagon. The front end resembled closely to the design of the 1971 Camaro with a similar grille, headlights, and bumper (via Hagerty).

Photo Credit: Mecum

In 1975, Chevrolet introduced the very interesting but unsuccessful Vega Cosworth model, featuring a high-revving 2.0-liter four-cylinder twin-cam motor with 110 HP. Although it wasn’t particularly fast or strong, the Vega Cosworth was good-looking. With an attractive black and gold paint job and unique wheels. The model was produced in cooperation with British engine engineering company Cosworth known for their Formula One engine.

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Chevrolet Citation X-11

The Citation X-11 is a very interesting car. It is a compact, front-wheel drive hatchback produced from 1980-1985. But it had a somewhat powerful V6 engine and muscle car looks. It would be best to describe this car as a fine line between an American hot hatch and a late-model muscle car since it features aspects of both segments (via Hagerty).

The Citation was a modern model that Chevrolet needed to fight import models. It came in a wide arrange of flavors. The X-11 featured a 2.8-liter V6 engine and 135 HP. Despite the fact it doesn’t sound much today, it was reliable power for the time. The X-11 had a few more tricks up its sleeves, such as a sports-tuned suspension, sharper steering, and better brakes. The X-11 can be differentiated from the outside by a unique bulged hood and trim details. The magazine testers of the day spoke highly of the X-11 as much more than just a stronger engine and appearance package. Unfortunately, this model is lost in the corridors of time and forgotten by all but die-hard Chevrolet fans.

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Pontiac Grand Prix 2+2

Domestic car buyers were surprised when Pontiac introduced an attractive 2+2 package for its popular luxury coupe in 1986. It was a muscle car the company had lacked since the late ’60s and an exciting version of a rather dull car the Grand Prix was in the ’80s (via Motor Trend).

Very similar to Monte Carlo SS Aerocoupe, the Grand Prix 2+2 used the same platform, rear glass, and rear spoiler intended for NASCAR races. Unfortunately, Pontiac didn’t provide 2+2 with exciting performance for street use since all cars got 305 V8 with 165 HP. On the other hand, Grand Prix 2+2 handled much better than the Aerocoupe. Since, gas-filled shocks, stiffer springs, sway bars, and high-performance tires were a part of the standard package. Pontiac produced this model for two years, and during that time it made 1225 cars.

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Pontiac Fiero

The story of the Fiero is one of the greatest “what if” tales of the American car industry. This classic sports car caused a big sensation in the early ’80s. Everybody expected another GTO from Pontiac. But they got a small sports car similar to something Italians would build. It was a bold move for Pontiac to introduce a compact, rear-wheel drive car with the engine positioned behind the driver and to pair it up with a five-speed manual transaxle gearbox (via Motor Trend).

For the standards of the day, this was the most advanced American production model. The Fiero’s appearance hyped customers, and with its cool and modern design and advanced technology, the initial response was more than good. For example, the 1983 sales figures topped over 130,000 examples. Unfortunately, Pontiac didn’t develop the Fiero, and early models needed to be better put-together. Engine power could have been better and the interior was cramped.

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Pontiac Trans Am 20th Anniversary Model

In 1989, Pontiac celebrated the 20th anniversary of its favorite muscle car, the Trans Am. They decided to introduce a limited run of 1,500 vehicles to commemorate the occasion. But, they wanted their anniversary edition to be unique and not just another decal and paint job. So Pontiac installed Buick’s 3.8-liter turbo V6 from GNX to create the fastest Trans Am of the decade (via Top Speed).

It turned out to be an extremely rare and expensive one. The white commemorative edition could accelerate 0.1 seconds faster from 0 to 60 mph than the GNX at 4.6 seconds. The reason was simple. It had a better weight distribution and gearing from a Pontiac gearbox. Today, those cars are rare and highly-prized collector’s pieces.

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Buick Roadmaster Wagon

The legendary Roadmaster name returned to Buick’s lineup in 1991 after a 33-year-long hiatus. Gracing the freshly styled luxurious sedan and station wagon model. The car was the same as other offerings from General Motors in the same class. However, the Roadmaster had some more luxury options and one interesting engine, which turned this comfy cruiser into a muscle car (via Motor Trend).

Buick engineers found a way to install Corvette’s LT1 5.7-liter V8 engine into Roadmaster’s engine bay. The LT1 had 300 HP in the Corvette, and the Buick had 260 HP, which was more than enough to turn this heavy wagon into a proper hot rod. Despite the curb weight of over 4400 pounds, this car could outrun many of the muscle cars of the day.

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Chevrolet SSR

During the mid-2000s retro craze, the Chevrolet development team came up with a crazy idea to produce a nostalgic two-seater convertible pickup with muscle car performance. The result was the SSR. A vehicle that looked different from any other car on the market, not necessarily in a good way. The 1950s-inspired design didn’t work well, so the SSR looked plain odd (via Car and Driver).

Despite many efforts to make the SSR appealing to the intended audience, Chevrolet managed to sell just around 24,000 of these oddballs in a painful realization that they needed much more than wild imagination to make that concept work. The SSR wasn’t a Corvette, and it wasn’t a truck. It was simply pointless overall.

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Cadillac CTS-V Wagon

For years, Cadillac was without a proper performance series needed to compete with BMW or Mercedes. But finally, the V-Series arrived. It was all that Cadillac lovers dreamed of powerful engines, world-class handling and suspension setups, and exclusive production. Even the competitors noticed when Cadillac rolled up the brand-new V-Series models (via Car and Driver).

Under the hood was a supercharged 6.2-liter V8 with 556 HP, making the CTS-V the most powerful performance sedan on the market. Cadillac produced three body styles, and CTS-V could be a sedan, a coupe, and, interestingly a wagon too. However, the wagon body style was something Cadillac buyers should have expected. The car was still a blast to drive and extremely fast. It was just that the majority of the customers turned to sedans or coupes. Some buyers even needed to be made aware that the wagon existed.

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Mystery Muscle: These Strange GM Muscle Cars Will Blow Your Mind

Oldsmobile Jetfire

Chevrolet Impala Z 11

1963 Corvette Grand Sport

Chevrolet Chevelle Z16

Oldsmobile Toronado GT

Chevrolet Chevelle “Heavy Chevy”

Chevrolet Laguna 454

Chevrolet Monza Mirage

Chevrolet Vega Cosworth

Chevrolet Citation X-11

Pontiac Grand Prix 2+2

Pontiac Fiero

Pontiac Trans Am 20th Anniversary Model

Buick Roadmaster Wagon

Chevrolet SSR

Cadillac CTS-V Wagon

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