The Buick Gran Sport or GS was a high-performance option package available on a number of Buick models, including the Riviera and Wildcat. A special version of one model was given the package's name as its model name.
The 1965 Skylark Gran Sport was the intermediate Buick. Although a V8 was already offered in the Skylark, the Gran Sport had the largest engine permitted by GM - a 400 in³ Buick V8. This engine was actually 401 in³ but called a "400" by Buick because that was the engine size limit set by General Motors. This engine produced 325 hp (242 kW) and 445 ft.lbf (603 Nm). Buick sold more than 15,000 Gran Sports that first year, and almost that many the next. It was renamed the GS 400 in 1967 and had a new "400" engine that was actually 400 in³. Sales fell somewhat in the face of hot muscle car competition, and Buick introduced the Stage 1 option for 1969. This limited (less than 1,500 cars in 1969) version produced 360 hp (253 kW) and 440 ft.lbf (597 Nm). The name Gran Sport was used again starting in the late eighties on the FWD Skylark model.
In 1967 Buick added a 340 in³ version, the Gran Sport 340 or Gran Sport California. It produced 260 hp (193 kW) and 365 ft.lbf (495 Nm), and less than 4,000 were sold. It was replaced the next year with the Gran Sport 350, and similar Gran Sport California; these used Buick's 350 in³ small-block engine. Sales of the little-brother Gran Sport doubled, and were up to almost 10,000 for 1970. The Gran Sport 350 outlived its big brothers, lasting until Gran Sport production stopped in 1975.
A baby brother Gran Sport 231 was produced in 1975.
The 400 was replaced for 1970 with the 455 in³ Buick V8, used in the GS 455. The base model V8 produced 350 hp (260 kW) and 510 ft.lbf at 2600 rpm. In the optional Stage1 trim it produced an underrated 360 hp (193 kW) and 510 ft.lbf (691 Nm) at a low 2800 RPMs. The real number was more accurately 415hp to 425hp due to the Stage 1 engine using a more aggressive cam and the standard heads were machined for larger valves to produce more power. The lower (false) horsepower numbers were used to get by General Motors Corporation imposed restrictions and Insurance Company concerns over increasingly powerful engines in affordable mid-size passenger cars, affectionately known as Muscle Cars. The Stage1 option, when paired with an automatic, included a firmer shifting Turbohydromatic 400.
There was also a very rare Stage 2 option produced. This was a dealer-installed package. If the car was ordered with the Stage 2 package, the parts were shipped with the car but were installed at the dealership. In general, it included special, larger port Stage 2 heads, matching headers, more radical cam, high compression forged pistons, Edelbrock B4B aluminum intake and other equipment for racing. Few were ever used on the street and Buick only ever factory assembled 3 Stage 2 test units. One of which was a factory GSX test mule with 4 speed manual transmission used for speed testing. The Stage 2 package's existence was not made public until 1972 when the Stage 2 parts could be ordered in any combination. There is little documentation about the Stage 2 cars.
Output and sales were down after 1970 largely due to reduced engine compression ratios and a change from gross to net horsepower ratings. In later years, air quality regulations further limited the power in part due to the addition of catalytic converters and single exhaust pipes.
GSX / GSX Stage1 was the optional high performance package available on the GS 455 starting in 1970. It was only available with the standard big block 455 engine or the optional Stage1 engine the first year. It was not a very popular model and only 678 GSX'S were produced in 1970, of those 400 were ordered with the Stage1 option. GSX performance was equal to that of the 'Hemi' 'Cuda with a much more luxurious car. This was partly due to the light weight build of the 455 which weighed roughly 150 lbs less than the Chevrolet 454. Quarter mile times in the 13.30s were reported in numerous magazines in 1970. Production dropped in 1971 to 124 total, and 44 in 1972. These numbers include the now available 350-4 bbl option, the standard 455, and the Stage 1 engines. The Buick 455 Big block V8 with stage one heads produces between 350-370 hp and 510 ft. lbs. of torque.
In 1970, the GSX option was available in only two colors, Saturn Yellow and Apollo White (in 1971 and 1972 other colors were available for the GSX). All GSXs had the distinctive full body length black stripe that crossed over the rear spoiler and was outlined in red pin stripes. A large area of the hood was also black with a hood mounted tachometer (Buick engineers disliked the hood tachometer because it was a Pontiac part) and black front spoiler. Also standard equipment were black bucket seats, floor shifter, wide oval tires, quick ratio steering and anti-sway bars. Some other options were automatic transmission or four speed manual.
After 1970, the GSX became an option that was available on any Gran Sport. Many GSXs survive to this day and can be seen at the Buick Gran Sport Nationals held annually in Bowling Green, KY in the middle of May along with many other examples of '60s, '70s and '80s Buick performance models.
The GSX and big-block V8 were dropped after 1974. In 1974, the GSX consisted of a trim package on Buick's small, X-bodied Apollo.
The Riviera GS was a high-performance version of the Buick Riviera, produced from 1965 through 1975.
In 1965, it was called Riviera GranSport and the later models were still officially called Gran Sport but showed GS badges instead of GranSport. Unlike the mid-size GS models, the Riviera and Wildcat GS package included a standard 3.42 positraction rear axle until 1973. The 1965 Riviera GranSport also came with a 425 cubic engine, dual carbs and dual snorkel chrome air cleaner. You could add H2 option (Ride and handling package) for even better road handling. Shorter gear ratio for steering, 1 inch lower suspension.
Another GS option package was available on the Buick Wildcat and Wildcat Custom, hardtop and convertible. The GS package included a 3.42 ratio posi rear, variable rate suspension springs, quick ratio steering box, heavy duty sway bars, and a switch-pitch turbo-hydramatic 400 transmission. The addition of the Y48 option gave the purchaser a pair of Carter AFB four barrel carburators, and finned aluminum valve covers on the 425 nail head engine. This was a one year only option. The Y48 option was delivered in the trunk and installed by the dealer.
In 1973-75 and in 1986, there was a Century Gran Sport.
From 1988 to 2004, there was a Gran Sport version of the Regal. The 1988 body style was available with the 3.8L Series I V6 producing 170 Hp. The 1997-2004 body style featured a 3.8L Series II supercharged V6 with 240 Horsepower.