Buick Secretly Built a 500-HP Race Engine to Beat the Hemi — Then Sold the Only Two Test Cars to Privateer Racers

A 1970 Buick GS hid an engine most muscle car fans have never heard of: an 11.0:1-compression 455 built for Super Stock racing and estimated past 500 horsepower, that Buick scrapped before a single customer could order one. Only two prototypes ever existed, and incoming emissions rules buried the program before it ever reached a factory build sheet.

Buick built a race engine in 1970 that was, on paper, faster than anything wearing a Hemi badge — and then made sure almost nobody ever got to buy one. The 455-cubic-inch Stage 2 package pushed compression to 11.0:1, swapped in forged pistons and reworked cylinder heads, and was built around a valvetrain tuned to spin past 7,000 rpm — numbers that belonged on a drag strip, not a dealership lot. Buick’s own engineers reportedly estimated the package at over 500 horsepower, with some dyno sheets said to show as much as 540. Only two cars were ever built to carry it: one sent quietly to a California dealership, the other handed to a pair of privateer drag racers who would campaign it for years afterward. Before Buick could decide whether to sell the thing to the public, incoming federal emissions rules arrived and killed the entire program. What survived is a story most muscle car fans have never heard.

The Buick Everyone Actually Bought Was Already Fast Enough

The video above, from the channel When Steel Spoke, retraces the short and strange life of the Buick GS Stage 2 — a factory engine package that never technically reached production, yet became one of the most-talked-about footnotes in muscle car history. The breakdown walks through why drag racers and Buick historians still argue about this engine more than fifty years after Buick quietly shelved it, piecing the story together from dyno sheets, dealer records, and interviews with people connected to the two cars that actually carried it.

To understand why the Stage 2 mattered, it helps to start with the Buick that collectors actually know: the Stage 1-equipped GS and GSX. The production Stage 1 package bumped the 455 to 360 horsepower and 510 pound-feet of torque, and it was quick enough that Motor Trend famously tested a four-speed Stage 1 car and called it the fastest muscle car the magazine had ever strapped a stopwatch to, with a quarter-mile run in the low 13-second range. Buick built only 678 GSX cars for the 1970 model year, nearly all of them in a tight production window between March and May. That alone makes the Stage 1 GSX a legitimate unicorn today. The Stage 2 is a different animal entirely — one that almost nobody actually got to own.

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The production GSX only reinforces how exclusive that car already was before Stage 2 ever entered the picture: Buick offered it in exactly two exterior colors for 1970, Apollo White and Saturn Yellow, both paired with black trim and the same black body striping. Roughly 187 were finished in white and 491 in yellow, out of the full 678-car run. That detail matters here because the Stage 2’s white test car was built on a GSX — meaning it almost certainly started life as one of that smaller, 187-car white batch before Reynolds Buick and Kenne-Bell got their hands on it.

A 500-Horsepower Engine Nobody Was Allowed to Buy

Buick’s engineers didn’t stop at the Stage 1. Behind the scenes, they were developing a heavier-duty version of the 455 meant for Super Stock drag racing rather than the street. The Stage 2 package raised static compression to roughly 11.0:1, added forged TRW pistons, redesigned cylinder heads for better flow, and strengthened the valvetrain to survive rpm well beyond what the production engine could handle. Estimates for the finished package run past 500 horsepower, and some reports on period dyno testing put the number closer to 540 — figures that, if accurate, would have embarrassed plenty of cars wearing more famous nameplates that same year.

The plan, as best as historians have pieced together, was to eventually offer the Stage 2 as an over-the-counter Super Stock racing package rather than a full production option — something a privateer drag racer could order through a dealer parts counter rather than something that showed up on a factory build sheet next to power steering and an AM radio. That alone tells you how far outside Buick’s usual playbook this engine was. Buick wasn’t chasing stoplight bragging rights with the Stage 2; it was chasing class wins at the drag strip, the same goal that pushed Mopar toward the Hemi and Chevrolet toward the LS6.

Two Test Cars, One Canceled Program, and a Scrapyard Ending

Only two cars were ever selected to carry and test the Stage 2 package. A white GSX was sent to Reynolds Buick in California, where tuner “Pappy” Kennedy and Jim Bell of Kenne-Bell worked on development. A second car, a red four-speed GS, went to privateer drag racers Doug Jones and Dave Benisek, who would go on to campaign a Stage 2-powered Buick in NHRA and AHRA Super Stock competition throughout the 1970s.

Then the program simply stopped. Looming federal emissions regulations were closing in fast on high-compression engines just like this one, and Buick made the call to cancel the Stage 2 before it ever became an official production option. The two test cars were sold off to the partners who had been running them, and the small remaining run of Stage 2 heads, pistons, and camshafts was quietly sold over the counter as performance parts for privateer racers rather than tied to any specific factory car.

The history gets murkier — and more interesting — from there. Some accounts describe the original GSX-based Stage 2 prototype as having toured the West Coast before being shipped back to Michigan, where a driver reportedly kicked a rod through the block during testing. The car was scrapped, but its hood was said to have been handed down to the Jones/Benisek race car, the one that kept campaigning in Super Stock years after the factory program died. Whether that red GS was truly a Stage 2 prototype, or simply a press car that inherited a prototype’s hood, is still debated among Buick historians today — which is exactly the kind of loose thread that keeps a story like this alive more than fifty years later.

Why a Canceled Engine Still Matters to Buick Collectors Today

For buyers and collectors, the Stage 2’s unresolved history makes it almost impossible to price the way a documented production car can be priced. A genuine Stage 1 GSX already commands serious money at auction thanks to its well-documented 678-unit run. A car with a legitimate, provable connection to the Stage 2 test program — parts, paperwork, or a chain of ownership back to Reynolds Buick or the Jones/Benisek team — would be in a different category entirely, since there is effectively no comparable sale to benchmark against. That scarcity is also why so many Stage 2 “tribute” and “recreation” builds have surfaced over the decades, built around genuine over-the-counter parts but without a verifiable factory connection; shoppers chasing this history should expect to lean heavily on documentation, not just a hood casting number or a seller’s story.

Most of what makes the GS Stage 2 special isn’t that it was fast — plenty of 1970 engines claimed big horsepower numbers that didn’t survive contact with reality. What makes it special is how close it came to never being documented at all. Unlike the GSX, which left a clear paper trail of 678 production cars, the Stage 2 exists almost entirely in dyno sheets, dealer memos, and the memories of a handful of racers and tuners who worked on it directly. There was no brochure, no factory build sheet, and for decades, no consensus on which surviving cars could legitimately claim a connection to the real prototypes.

That makes the Stage 2 a rare case where the muscle car era’s most interesting engineering didn’t happen in the showroom at all — it happened in a back lot in California and on a drag strip in Super Stock competition, built by people who never expected anyone to be writing about it fifty-plus years later. For a brand that rarely gets credit alongside Chevrolet, Dodge, and Pontiac in muscle car conversations, it’s a reminder that Buick was willing to chase genuine race-engine performance — it just never got the chance to sell it.

Watch the full video above and let us know your thoughts in the comments.