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1970 Buick GSX/GSX Stage 1 Specs and History

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Looking back into the classic musclecar era, there are plenty of well-known contenders when it comes to vehicles you should know. But if you stick with the common denominators, mainly of the Mustang, Camaro and Chevelle variates, you will inevitably miss out on a whole section of the musclecar world that deserves more attention than it gets. One such case is the 1970 Buick GSX/GSX Stage 1. A mighty machine in what some would consider sheep’s clothing, after all it is still a Buick, this fantastic car is our choice for this month’s Musclecars You Should Know!

Built off of the Buick Gran Sport (GS) platform, the GSX made its debut in 1970. A step up from even the GS 455, also offered for the first time in 1970, the GSX was marketed as the high-performance GS package, complete with a 455ci engine and plenty of unique performance-related additions.

Meant to attract more business for Buick dealerships, the GSX performance upgrade was only available on the GS 455s and went on to compete against the likes of the Olds 4-4-2 W-30 cars and the GTO Judge from Pontiac.

And having a displacement of nearly 456ci between its fenders, it managed to come out on top as far as engine size was concerned, even beating out the Pontiac 455ci engine by a mere 0.152ci.

Tied to the massive 455ci powerhouse were performance numbers that couldn’t be argued with. With the standard 455, customers could expect to get 350hp out of their cars at 4,600RPM and an astonishing 510 lb-ft of torque at 2,800RPM. Thanks to a higher-lift camshaft and slightly richer jets, earned with the extra $100 to $200 price tag (some sources say the Stage 1 option was only $115 while others site a slightly higher $199 price tag), the GSXs equipped with the optional Stage 1 engine produced the same amount of torque but an advertised 360hp, which is actually believed to be highly underrated.

Although neither horsepower number from either engine is all that impressive and didn’t exceed the power of some of Buick’s GM counterparts back in the day, the torque rating on the engine made the Buick 455 the reigning champion for the most torque of any mass-produced American musclecar manufactured at the time.

It wasn’t until 2003 and the potent Dodge Viper that the Buick GSX lost its title.

To produce so much torque and a respectable amount of horsepower, the base 455ci engine came with a compression ratio of 10.0:1, valves sized 2.005 inches on the intake side and 1.630 inches on the exhaust side, as well as a camshaft with a lift of 0.3891 inches for the intake and 0.4602 inches for the exhaust. The standard engine also featured a 290 degree intake duration and a 322 degree exhaust duration with an overlap of 67 degrees.

Giving the Stage 1 GSX its added power was a 10.5:1 compression ratio, valves sized 2.120 inches on the intake side and 1.745 inches on the exhaust side, as well as richer jets in the engine’s 750cfm Quadra-jet carburetor. Instead of the standard 455ci cam lift, the Stage 1 engine featured a lift of 0.490 inches on both the intake and exhaust sides. Fittingly, the Stage 1 engine also featured a 316 degree intake duration and a 340 degree exhaust duration with an overlap of 90 degrees.

Supporting the base 455ci engine in the non-Stage 1 GSXs was a close-ratio Muncie four-speed with a Hurst linkage, while the Stage 1 cars were equipped with a special Turbo Hydra-Matic 400 with a three-element torque converter to make things even more interesting.

These were just the base suggestions, however, as both the GSX and GSX Stage 1 cars both came with options for either an automatic or manual transmission.

Supporting the brunt of the car’s torque was a rearend gear ratio ranging from 3.42:1, for the GSX cars, to 3.64:1 in the Stage 1s. If a car was equipped with the air conditioning the car received the less potent 3.42:1 rearend gear ratio.

Both the GSX and Stage 1 cars were equipped with a 1-inch anti-roll bar in the front, stout shocks with 1-inch diameter pistons, and heavy-duty rear lower control arms. The cars also featured a rear anti-roll bar, upgraded bushings, 450lb springs in the front, 144lb springs in the rear and a quick-ratio steering box.

Braking came compliments of standard 11-inch vented rotors as part of a power disc setup in the front and 9.5-inch brake shoes in the rear for the Stage 1 cars. Four wheel drums were also available and included heavy-duty aluminum components with steel linings in the front. Either way, the brakes sat behind chrome-plated 15×7-inch Rallye wheels in the standard form. These wheels were wrapped in popular G60-15 tires for added traction.

Although we all know performance numbers are well and good, they mean nothing if they can’t be backed up on the street or track. But the GSX doesn’t disappoint with a zero to 60mph time of just 5.8 seconds and a quarter mile time of 13.38 seconds with a trap speed of 105.5mph, according to the Motor Trend report on the car in 1970.

If the car was equipped with an automatic transmission, causing the car’s base weight to increase from 3,874lbs to 3,919.7lbs, its performance numbers were only slightly less.

We would imagine the addition of the Stage 1 engine upgrade, an additional 2.4lbs compared to standard equipment, would only slightly improve the car’s acceleration times with the extra 10hp rather than drastically improve things. Although power is power and you can’t argue with more ponies under the hood.

While both the GSX and Stage 1 cars were about performance, they didn’t fall flat in the aesthetics department. For just over $1,000 on top of the GS 455 price, customers got an exclusive GSX ornamentation package, including a distinct black full-length body stripe, rear spoiler, blacked out hood, hood tachometer, a black front spoiler and GSX badging. Buick even boasted about the addition of sport mirrors to the GSX package.

Only offered in Saturn Yellow and Apollo White in 1970, the GSX/Stage 1 cars came standard with black bucket seats and a floor shifter.

No more than the two exterior colors and black interior color were offered on GSX cars in 1970, although that changed for the 1971 and 1972 models.

In 1970, although the car was manufactured as a direct competitor for 4-4-2s and Chevelle LS-6s as well as to bring more business to Buick, the GSX was not very popular. In fact, only 678 GSXs were built with just 278 equipped with the standard 455ci engine and the other 400 equipped with the Stage 1 engine.

According to official Buick documentation, 491 GSXs were produced in Saturn Yellow and 187 in Apollo White. Of the 678 total, only 199 cars were produced with four-speed manual transmissions while the other 479 were produced with the optional automatic transmission.

Ironically enough, although even fewer GSX cars were built in 1971, with only 124 built, and 1972, with only 44 built, it is the 1970 GSX models that are the most highly sought after today.

The 1970 Buick GSX and GSX Stage 1 cars have to be by far one of the coolest Buicks out there. Not only are they rare and mighty neat looking, they’re also equipped with one of the highest torque producing engines ever put in a mass produced musclecar still to this day. What other late 1960s and early 1970s cars can claim all that?