What Is A GM G-Body? (And 5 Iconic Muscle Cars That Used It)

The mid-1970s saw some changes that made this era challenging for muscle car manufacturers. The U.S. government — in its bid to control air pollution and improve fuel efficiency — rewrote the regulatory book for automakers when it passed the Clean Air Act of 1970. This prompted most American car companies to downgrade and redesign their engines in order to comply. Just as the industry was coming to terms with the new emissions regulations, the Organization of Petroleum Exporting Countries (OPEC) embargo in 1973 all but cut off crude oil supplies to many countries.

The cost of oil jumped from $3 to $12 a barrel, and gas prices jumped from $0.35 in 1970 to $0.50 per gallon in 1974 (a 43% increase). Because of their higher power outputs, muscle cars from the 1960s and early '70s were associated with riskier driving and, consequently, accidents and fatalities. Thus, muscle car owners were considered high risk for car insurance by companies and were accordingly charged higher premiums to insure. This sadly increased running costs for drivers with thirsty, high-horsepower V8s. 

As rising insurance costs and fuel shortages became critical problems, buyers began to shift towards more efficient options from abroad. American automakers had to respond, and for General Motors, that came in the form of the G-body platform. The GM G-body was introduced in 1978 as a versatile, intermediate platform that was designed to be lighter than the A-body chassis it replaced. This would enable GM to increase the fuel efficiency and performance of its best-selling cars. Here are five iconic muscle cars that used the GM G-body platform.

One of the highest horsepower muscle cars of the 1980s, the limited-production Buick Regal Grand National Experimental (GNX) is perhaps GM's greatest source of pride in the '80s. All 547 units of the GNX began life as a 1987 Buick Regal Grand National, but were adorned with an interior trim package before making their way to ASC/McLaren Performance Technologies to be given the full GNX treatment. Beneath the hood, they had the same 3.8-liter turbo V6 as  the regular Buick Grand National. 

But instead of 245 horses and 335 lb-ft of torque like its 1987 siblings, the GNX's V6 made an impressive 276 hp and 360 lb-ft. This was thanks to a raft of engine tweaks, including an improved turbocharger, higher-flow heads, and a less restrictive dual exhaust. Engineers also redesigned the rear suspension, considerably stiffened the body, and upgraded all four wheels to 16 inches in comparison to the 15-inch wheels on the regular Buick Grand National. The result was a car that Motor Trend tested at 4.7 seconds from 0-60 mph. This was faster than the likes of the Ferrari Testarossa (5.0 seconds), Chevrolet Corvette (5.8 seconds), Ford Mustang LX (6.0 seconds), and Chevrolet Camaro IROC-Z (6.3 seconds).

With the original 1968 Hurst/Olds turning 15 in 1983, Oldsmobile launched a celebratory limited edition to commemorate the anniversary. The new Hurst/Olds was based off the Oldsmobile Cutlass Supreme, which was underpinned by the GM G-body platform. As per usual with celebratory models, the 1983 Hurst/Olds received distinctive styling. In this case that meant a two-tone black and silver paint job with red pinstriping. A bulging hood up front — as well as dual exhausts and a rear spoiler out back — further highlight the Hurst/Olds for the unique muscle car it is.

Chrome 15-inch wheels shod with Goodyear Eagle GT tires were also part of the package. Under the hood, Oldsmobile offered a 5.0-liter (307 cubic-inch) V8 with aluminum intake manifold, 825-cfm four-barrel Rochester carburetor, and modified camshaft. With these upgrades, the V8 produced 180 horsepower and 245 lb-ft of torque. Despite the relatively modest power, the Hurst/Olds sold well thanks in part to its aesthetic appeal, and popular demand resulted in the car returning for 1984.

The SS-badged Chevrolet El Camino Choo Choo Custom is another outstanding muscle car that was built on the '80s GM G-body. This was a special appearance package made for Chevrolet by Choo Choo Customs between 1983 and 1987. The Chattanooga, Tennessee shop is widely known for its incredible van conversions, but took a detour to spruce up the El Camino. The conversion managed to inject sporty and luxurious cues, with a Monte Carlo SS-style front end, side exhaust skirts, and aluminum wheels combining to make the El Camino SS an instant design icon.

Any changes made to the swoon-worthy, Choo Choo-tuned El Camino SS weren't directly related to performance, though, as its 5.0-liter V8 only produced 150 horsepower. That didn't dull the Choo Choo Customs El Camino's sparkle, thankfully, and the vehicle continues to enjoy a strong following to this day. Well-maintained examples fetch upwards of $20,000 on the secondhand market. Chevy claims that 5,000 El Caminos were converted by Choo Choo Customs, but some sources claim the number is less than half that. What is known is that 861 were made in 1987, the last year for the El Camino.

The Regal survived until it was the last non-SUV sold by Buick, but the 1986 Regal T-Type was something special. Special here means the "quickest and fastest production car built in America," according to Hot Rod magazine. That honor is owed to a 3.8-liter turbocharged and intercooled V6 engine which generates 235 horsepower and 330 lb-ft of torque. That's an 18% increase in horsepower and 10% more torque than the non-intercooled 1985 model.

Output is directed to the wheels via a slick Turbo Hydra-matic 200-4R automatic transmission, and with that, the Regal T-Type could scoot to 60 mph in 5.85 seconds and cover the quarter mile in 14.30 ticks at 98.4 mph. But eating up miles wasn't the only thing the T-Type was renowned for. It handled well, too, pulling 0.80 g on P215/65R-15 Goodyear Eagle GTs. The huge levels of grip go hand-in-hand with very strong brakes, with the T-Type able to stop from 60 mph in 141 feet.

After a 12-year hiatus, Chevy brought the Monte Carlo SS back in 1983 as part of the fourth generation, which was introduced in 1981. The new Monte Carlo SS featured desirable bits such as special front-end styling, European color-coding, and SS-specific wheels and tires. This was part of Chevy's plan to make it stand out from the rest of its G-body cousins. The 5.0-liter V8 produced 175 horsepower in 1983 but got a 5-horse bump the following year.

Buyers loved it. Monte Carlo SS production for the 1983 model year totaled 4,714 units, and those numbers were just the beginning. The following year, Chevy sold more than 24,000 units of the Monte Carlo SS, and sales of all Monte Carlo models jumped from 96,000 to 136,000 units. By 1985, 35,000 of the 119,000 Monte Carlos sold (about 29%) were SS models. Even today, the fourth-generation Monte Carlo SS remains in high demand, with sale prices often exceeding $20,000 .