276 bhp, 231 cu. in. turbocharged and intercooled V-6 engine with sequential multi-port electronic fuel injection, GM Turbo-Hydramatic 200-4R automatic transmission with overdrive, independent front suspension with unequal-length A-arms, coil springs and anti-roll bar, live rear axle with four-link rear suspension including coil springs and stabilizer bar, and front disc, rear drum hydraulic brakes. Wheelbase: 108.1"

- One of only 547 built

- Built by ASC/McLaren with Garrett turbocharging

- Never road-registered, just 278 miles from new

- Offered in virtually untouched, “time warp” condition

Since American “big block” V-8s were largely extinct by the mid-1970s, Buick engineers experimented with turbocharging the 231-cubic inch V-6, and their first high-profile effort, a 307-hp Century in 1976, was the first V-6-powered Indianapolis 500 pace car. The chiseled lines of the new-for-1978 Regal helped Buick take the NASCAR manufacturer’s title for 1981 and 1982, and to celebrate, the first Grand National Regal appeared in 1982.

The option returned in 1984, now only with a turbocharged V-6 engine, an all-black exterior, aluminum wheels, special seats, high-performance underpinnings and unique badges. Steady development and intercooling raised output to 245 hp by 1986, creating America’s quickest production car.

As Grand National production neared the end, Buick authorized a limited run of 547 specials, designated GNX. Built by ASC/McLaren, the builders of the 24-valve Buick turbo V-6 engines for Indy, the GNX used a high-performance Garrett turbo, an improved intercooler, revised engine and transmission calibration and lower-restriction exhaust. Output jumped to over 276 hp with 360 ft-lbs torque. Larger tires, special alloy wheels, a rear-axle torque arm and a Panhard bar plus a stiffer frame were GNX-specific upgrades. Front-fender vents and special analog instruments completed the package, which also included a full load of factory options.

Aside from extreme rarity, this very special GNX has never been road-registered and shows about 278 miles from new. Offered with a recent full service by RM Auto Restoration, it remains in “time warp” condition, down to the factory-original audio system. On display from new until recently at the Auto & Technik Museum in Sinsheim, Germany and a former part of the UK’s Hooper Corporate Collection, this GNX is a great example of one of the fastest and rarest American performance cars.