The GSX came in Saturn Yellow or Apollo White with spoilers fore and aft and special emblems. Nestled beneath that sinister hood was an engine with the highest torque rating of any American car until the Dodge Viper eclipsed it in 2003. In 1970, the Buick 455 produced 510-lb.ft. of torque at 2,800 rpm and 350hp at 4,600 rpm. The more powerful Stage 1 produced the same torque rating, but had 10 more horsepower according to the factory. Independent dynos placed the GSX Stage 1's horsepower at somewhere between 390 and 395hp.

The Stage 1 engine option consisted of a more aggressive camshaft, higher compression, unique cylinder heads with larger (2.13" intake and 1.755" exhaust) valves, a specially tuned 4 barrel Quadrajet carburetor, more aggressive ignition timing, a larger 5/8 inch oil pickup tube and a higher numerical final drive. The engine was available with either a firmer shifting Turbohydromatic 400 or a Muncie M-22 "rock crusher" 4 speed and a standard 3.64:1 Positrac axle ratio. Stage 1 cars equipped with air conditioning received a 3.42 diff ratio.

There was also a rare Stage 2 option produced. This was a dealer-installed package first offered in 1969. It included a cam, headers, intake manifold, high compression forged pistons, hollow pushrods, and some calibration changes to the ignition and carburetor. If the car was ordered with the Stage 2 package, the parts were shipped in the trunk of the car. In 1970 the Stage 2 package included special D- Port exhaust port Stage 2 heads, matching Kustom brand headers, a radical cam, high compression forged pistons, Edelbrock B4B aluminum intake, Holley carburetor, and other equipment for racing.

Few Stage 2s were ever used on the street and Buick only ever factory assembled 15 Stage 2 test units. One of which was a factory GSX test mule with 4 speed manual transmission used for speed testing. That GSX test mule was equipped with 4.78 gearing and was driven on the streets and tracks on the west coast. 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 12 Stage 2 cars that were sold. One was campaigned by Kenne-Bell/Reynolds Buick and the other was known as the Jones-Benisek car. The Jones/Benisek car is known to have been delivered as a Stage 1 car with all the Stage 2 components in the trunk in GM boxes.

There were 678 GSX cars built in 1970. Of these, 491 were yellow and 187 were white according to the GSX Registry. Of the 678 cars, 199 had four-speed manual transmissions and 479 were automatics. 278 had standard 455 engines, while the other 400 had the Stage 1 option. That option included: a hood tach; stiffer shocks and suspension pieces; heavy-duty cooling; power front disc brakes and G60x15 tires on Buick Rallye chrome-plated wheels. Other GSX specific standard equipment included: Power front disc brakes; 3.42:1 ratio posi-trac rear end; special front stabilizer bar; heavy-duty front and rear shocks and a heavy-duty rear anti-roll bar.

Production:

GS 2D Hardtop: 9,948
GS455 2D Hardtop: 8,732
GS455 Convertible: 1,416



Engines:

GS350: 350 V8 315 bhp @ 4,600rpm, 410 lb-ft @ 3,200 rpm.
GS455: 455 V8 350 bhp @ 4,600rpm, 510 lb-ft @ 2,800 rpm.
GS455 Stage 1: 455 V8 360 bhp @ 4,600rpm, 510 lb-ft @ 2,800 rpm.



Performance:

GS455 Stage 1 - 455/360: 0-60 in 6.5 sec, 1/4 mile in 13.7 sec @ 101 mph.

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