Buick Gran Sport

In 1965 Buick entered the muscle car market with its Gran Sport. Like Pontiac, Buick started with its version of the intermediate A-Body chassis, the Skylark, and stuffed a big V8 engine in it. With a 340-cubic-inch engine it qualified as a member of the muscle car class. The Gran Sport Stage I model had a 455-cubic-inch engine with a speed package giving 360bhp.
With its sedan styling and small-block engine, the Buick GS 340 only triggered the buy impulse to 3,892 buyers in 1967. The baby-boom generation just didn't want small-block engines producing only 260 horsepower.
Gran Sport sales continued to flatline. The addition of a functional fresh-air induction system in 1969 wasn't enough to overcome the Gran Sport's frowning-octogenarian profile, and sales fell another 40 percent that year. With total Gran Sport sales of just 8,132 units in 1969, Buick's position in the youth market couldn't have been grimmer if division stylists had drilled portholes in the car's unfortunate front flanks.
The Stage I package included a high-performance camshaft and special four-barrel carburetor, also Hurst floor-shift four-speed transmission. Most GS Stage I models were coupes, but some convertibles were made for the 1970 season. Since the Buick Gran Sport's dash didn't lend itself to a circular tach. Buick designers mounted it in the floor counsel in front of the shift lever.
Buick had held high V8 performance ability for decades and their Fireball Eight, an inline eight-cylinder - a design known as the "straight eight" - had powered performance cars like the Century since the 1930s. Throughout the intervening years, Buick had always kept sporty performance cars in its lineup and the division jumped at the opportunity to battle Pontiac in the intracorporate muscle car wars that raged within General Motors after the introduction of the GTO.
When GM relaxed the ban on larger displacement engines in the corporate A-body chassis for 1965, Buick, followed the lead of Chevrolet and Oldsmobile and mounted a 401-cubic-inch engine in its Gran Sport, which was a GTO-like option package for the divisions A-body car, Skylark. Although the engine's 325 horsepower put it at the bottom rung of the A-body performance ladder, the engine made up for its relative lack of peak power with a prodigious torque output of 455 ft-lb. This made the Gran Sport a real tire shredder when taking off from a stoplight. Smokey burnouts impressed the neighborhood kids a lot more than did esoteric dyno charts. Besides, if an owner wanted to do some serious drag racing with this Gran Sport, he could purchase a dual carburetor manifold and a pair of four-barrel carbs from his Buick parts man.
With the potent 455-cubic-inch V8 in the GSX trim with a Stage I package, this engine generated a massive 510 ft-lb of torque. A quick glance at the spec sheet didn't reveal the 455-cubic-inch engine's greatness. The engines 350-horsepower rating fell below the ratings of its big-engined competitors, but given the artificially low ratings of the period, this number had little relationship to the engine's actual output.
To get an idea of how underrated the engine was, consider that the same engine in the same state of tune was rated at 370 horsepower when mounted in the Buick Rivera, and even that rating was low. The Gran Sport GS455 had one of the highest torque ratings of any engine ever to power a muscle car.
Unfortunately, like all GM muscle cars, Buick lowered the compression ration of the GSX in 1971.
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