Sales fell somewhat in the face of increasingly higher-performance and more popular muscle cars from other marques, including corporate stablemates Pontiac GTO, Chevrolet Chevelle SS and Oldsmobile 442, when compared to those from the more conservative and luxurious Buick.

The merchandising creation of the West Coast's Mickey Garrett, the California GS became one of Buick's entries into what is now often known as a junior musclecar.

The intent of these autos were to provide the visual impact of the era's supercars with the low maintenance and price of a more economical car, while maintaining reasonable performance levels.

The drivetrain included Buick's new for '68 350-4 V8 with 10.25:1 compression and Rochester (GM) 4GC Quadrajet four-barrel (four-choke) carburetor,[4] producing 280 hp and 375 lb·ft of torque.

The two-speed[3] Super Turbine 300 transmission (driving a 3.23:1 rear axle gear, designed for highway cruising)[3] and bench seat interior were again the only choices.

Buick also added chrome plated wheels and air cleaner lid to the two-door thin pillar coupe.

Vinyl tops, as with previous years, were standard fare with the California's distinctive GS logo on the sail panel.

Using Hale's Trap Speed formula, this result indicated actual "as installed" peak HP of approximately 360 SAE Net (ironically the same as its advertised Gross Figure, meaning this engine was very conservatively rated for that time period).

[citation needed] The Stage 1 engine option used cylinder heads that, while using raw castings of the same pattern as all of the other Buick 455s sharing the same model year, were machined differently in order to accept larger valves (2.13" intake and 1.755" exhaust), and to produce smaller compression chambers for increased static compression ratio.

The option also included a more aggressive camshaft, a specially tuned 4-barrel Quadrajet carburetor, more aggressive ignition timing,5/8 inch oil pickup tube and a higher numerical final drive, and was available with either Turbo Hydra-matic 400 3-speed automatic transmission, or a Muncie M-22 4-speed manual transmission (although it was later discovered, and confirmed, that one 1970 GS Stage 1 convertible was produced with a 3-speed manual and a standard 3.64:1 Positraction axle ratio).

All used 2 bolt main bearing caps; the oiling system was undersized for high-rpm use (including Stage 1 engines) and thin walls in the lifter valleys promoted cracking.

Stage 1 controversy has prompted several contests to settle the issue; it remains an unsettled matter and has been a great boon to car magazine sales over the years.

It included a cam, headers, intake manifold, high compression forged pistons, hollow pushrods, and some calibration changes to the ignition and carburetor.

Output and sales for the assembly-line cars 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.

The GSX was Buick's attempt to increase showroom traffic on a newly designed Skylark body style for 1970 which started off slow but sales improved.

Due to the late introduction of the GSX, a very special prototype was displayed at the Chicago Motor Show in February 1970 to test consumer reaction.

This particular GSX had Mother Of Pearl white paint, a special fiberglass/steel ram air hood with unique modified hood scoops, one-off 3 piece rear spoiler and a prototype front spoiler, custom multicolored leather interior featuring checkerboard black and white X patterned seats and door panels.

The impressive performance is partly due to the light weight of the 455 which is roughly 150 lb (68 kg) less than the Chrysler 426 Hemi or Chevrolet 454.

At 510 lb-ft the Buick 455 produced the highest torque output of any American production performance car, a record held for 33 years until finally surpassed by the Series 2 V10 Viper in 2003.

[citation needed]The 1970 Buick GSX has, without doubt, the most extensive list of standard equipment high performance features of any classic era muscle car.

You could buy a poorly optioned Chevelle SS, a leaf-sprung, bench seat Hemi Roadrunner or even a Pontiac GTO Judge with the smaller 400ci engine and drum brakes, but there is no such thing as an under-equipped 1970 GSX.

The addition of the Y48 option gave the purchaser a pair of Carter AFB four barrel carburetors, and finned aluminum valve covers on the 425 nailhead engine.

Both engines were also mated to catalytic converters for the first time this year, which mandated the use of unleaded gasoline and precluded the availability of true dual exhaust systems.

Performance versions of the Century (and its companion Regal line) and Riviera would return in the late 1970s with the advent of Buick's turbocharged 231 V6 introduced in 1978 on the Century/Regal intermediates and the full-sized LeSabre Sport Coupe and then the newly introduced front drive Riviera in 1979 for the "S-Type" which later became the T-Type, a moniker that would ultimately replace the GS badge for sporty/performance Buicks in the early 1980s.

The Century GS model returned in 1986 for what was now Buick's front-drive intermediate-sized car (Regal continued as a coupe on the 1978-vintage rear-drive G-body until 1987).

The Gran Sport option generally contained the following items: Beginning in late 1990, the 3.8L (231 cu in) Series I V6 producing 170 horsepower (130 kW) was available.

Since the parts were available from SLP over the counter for many years, there have been quite a few Regal GS sedans that have been cloned into a GSX for both appearance and performance purposes.

This front-wheel drive sedan GS features Buick's Interactive Drive Control System with GS mode, a choice of an FGP Germany F40-6 six-speed manual or Aisin AF-40 (G2) six-speed automatic transmission, high performance brakes with Brembo front calipers and high performance strut (HiPerStrut) front suspension.

The new Regal is equipped with a GM LGX V6 3.6 producing 310 horsepower paired with a 9-speed automatic transmission yielding acceleration from zero to 60 mph in under six seconds.