The Buick Nobody Saw Coming: This 1970 GSX 455 Stage 1 Out-Ran Every Car Motor Trend Tested That Year

Buick wasn’t supposed to build a car that could embarrass a Hemi, but the 1970 GSX Stage 1 in Saturn Yellow did exactly that — including a documented 1984 grudge race where a GS beat two different Hemi-powered cars in a single day. Only 678 were built, and Motor Trend once clocked one as the fastest car it tested all year. Watch the full story behind the numbers.

Buick spent most of the muscle car era building comfortable, quiet land yachts for buyers who wanted luxury and isolation from the road, not quarter-mile bragging rights against their neighbors. Then, for essentially one model year, the brand built something that earned the nickname “Hemi Killer” among enthusiasts — and the story behind that nickname involves a magazine road test, a long-running interbrand rivalry, and a driver willing to prove his car’s reputation twice in the same single day. This 1970 GSX Stage 1 in Saturn Yellow is one of only 678 ever built, and according to the people who actually raced one back when they were new, it deserved every bit of the outsized reputation that followed it.

678 Built, and the Numbers Were Understated

Buick officially rated the GSX Stage 1’s 455-cubic-inch V8 at 360 horsepower and 510 foot-pounds of torque, numbers that even at the time were widely understood within the industry to be conservative — a common practice during an era when insurance companies had begun pricing policies directly off advertised horsepower figures, giving manufacturers a strong financial incentive to underrate their most powerful engines. In practice, the Stage 1’s real-world performance routinely and dramatically outran what its comparatively modest factory rating suggested it should be capable of on paper.

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Motor Trend’s Fastest Test of 1970

That real-world performance eventually showed up in print for everyone to see: Motor Trend clocked a 1970 GS Stage 1 running the quarter-mile in 13.35 seconds at 105.5 mph, a result the magazine specifically flagged as its single quickest test of the entire 1970 model year — beating out plenty of cars carrying far bigger, more headline-grabbing advertised horsepower numbers from Detroit’s other manufacturers that same season.

How the GSX Earned the Name ‘Hemi Killer’

The “Hemi Killer” nickname traces back to one specific, well-documented event rather than casual bragging. According to GSCA founder Richard Lasseter, he beat a braggart’s 1970 GTX Hemi in a straight-up race, then turned around and beat a friend’s Hemicuda the very same day in December 1984, after personally driving his own Stage 1 GS some 275 miles down to Gainesville Raceway in Florida specifically to settle the argument. The full story ran in the March 1985 issue of Muscle Car Review, cementing a nickname that Buick loyalists still repeat with pride more than four decades later.

The Stage 1 Package Explained

“Stage 1” was never just a marketing sticker slapped on the fender — it represented Buick’s genuine, factory-blessed performance package layered directly onto the standard 455, adding a revised camshaft profile, a larger carburetor, and considerably stronger valve springs. Together, that combination represented the highest state of factory tune Buick offered anywhere in its 1970 lineup, available to any buyer willing to check the right option box on the order form.

Why It Weighed More and Still Won

Commenters consistently note that the GSX ran noticeably heavier than most of its direct muscle car rivals, yet still managed to out-accelerate a great many of them regardless — a useful reminder that raw torque, not simply horsepower-to-weight ratio alone, is what actually let the GSX punch so far above its considerable curb weight class. The Stage 1’s torque figure in particular was genuinely enormous relative to almost anything else on the market that year.

Saturn Yellow and the GSX Stripe Package

Visually, the GSX package paired a bold Saturn Yellow paint finish with black striping, a rear spoiler, and dual functional hood scoops — a deliberate, calculated departure from Buick’s usual reserved, understated brand image, specifically designed to visually announce exactly what the Stage 1 badge actually meant sitting underneath the hood before a single wheel ever turned.

A Brand Loyalty That Still Runs in Families

The comments reveal just how deep this particular brand loyalty runs across generations: one commenter describes being the son of a dealer who sold both Pontiacs and Buicks continuously from 1964 all the way through 2008, with a specific, lasting soft spot reserved for what he calls “Buick’s Torque Monsters” from the 1968-72 window specifically. That kind of genuine generational attachment, persisting decades after the cars themselves stopped being manufactured entirely, says as much about the GSX’s real legacy as any single magazine test ever could.

Why Buick Built a Muscle Car At All

It’s worth asking why Buick built a genuine muscle car at all, given how thoroughly it clashed with the brand’s broader identity at the time. The answer lies largely in internal GM politics: with Pontiac’s GTO and Oldsmobile’s 442 both already established and selling well, Buick’s own dealer network pushed corporate leadership hard for a competitive answer of its own, arguing that younger buyers were being lost entirely to sister divisions offering genuine performance options that Buick simply didn’t have on its own showroom floor.

What a GSX Stage 1 Commands Today

Today, a documented, numbers-matching GSX Stage 1 in genuine, unmolested condition routinely commands six-figure sums at major collector auctions, a price level that reflects both the car’s extreme rarity — just 678 built in Stage 1 trim — and its increasingly well-known performance history. For a brand not usually associated with headline muscle car money, that kind of valuation is itself a quiet testament to exactly how far the GSX’s underdog reputation has traveled since 1970.

A Brief Window That Closed Almost as Fast as It Opened

The GSX also arrived at an oddly precarious moment for Buick’s broader lineup, sandwiched between the brand’s traditional luxury cars and the looming reality of tightening emissions and insurance pressure that would gut the entire muscle car segment within just a few short years. Viewed in that light, the 1970 GSX Stage 1 looks less like the start of a new performance direction for Buick and more like a brief, deliberate high point the brand reached right before the door closed on that kind of car entirely — which only adds to why surviving, unmodified examples are treated with such reverence by collectors today. It was a peak, not a beginning.

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