The golden era of American performance gave us countless , but the 1970 Chevrolet Chevelle SS is generally believed to rule the roost – and rightly so. The 454-cubic-inch LS6 V8 was rated for an astonishing 450 horsepower at the time of its debut, and the block backed that figure up with an equally impressive 500 lb-ft of torque. As such, the Chevrolet Chevelle and its raw power, aggressive styling, and rumbling exhaust note became synonymous with the muscle car era. For many, it represents the pinnacle of performance before the muscle car era was curtailed by tightening emissions regulations and rising insurance costs.While the Chevelle was certainly a force to be reckoned with, there was actually another muscle car that surpassed its power output. Back in the day, it was the brand to beat on the strip, and this vehicle was well-known for its straight-line speed. However, time has softened the automaker’s reputation, and younger enthusiasts have never known it to be a true performance presence. As a result, this muscle car goes overlooked compared to the likes of the Chevrolet Chevelle SS 454. We’re here to set the record straight. The Buick GS Stage II Was The Most Powerful Muscle Car In The '70s Mecum The most powerful muscle car of the 1970s technically came from Buick, as the automaker built two prototypes for its 1970 GS 455 with a Stage 2 performance package. As an even more potent follow-up to the immensely powerful Stage 1, it was designed for absolute drag strip domination, and it was rated for an authoritative 500-plus horsepower.Unfortunately, Buick pulled the plug on the program before it was made available for public sale, so no other factory-equipped cars exist today. However, Buick did offer the parts as over-the-counter upgrades for privateer racers and insistent customers, so road-legal Stage 2 conversions can be found – if you're patient. Buick's Stage 1 Was Underrated From The Factory Mecum Back in 1969, MotorTrend tested a Buick GS 455 equipped with a Stage 1 kit ahead of launch and managed some seriously impressive performances, hitting 60 mph in a mere 5.5 seconds before running the quarter-mile in 13.38 seconds at 105 mph. The feats made it the fastest muscle car the magazine had ever tested, and few competitors of the day could hope to match those numbers. Amazingly, however, Buick only claimed 360 horsepower from the Stage 1-equipped car. Most sources today agree that the number was conservative and picked to keep insurance agents happy; even the LeSabre and Wildcat delivered some 370 horses, so the GS likely made at least a healthy 400. Stage 2 Options Took Performance To The Next Level MecumBuick's Stage 1 options included low-restriction dual exhausts, a high-rpm valve train, and a special hydraulic lifter cam, as well as a revised oil pump, a 3.64:1 limited-slip axle, and a higher shift-point automatic transmission. Though those made for some noticeable differences in GS performance off the line, not even a 13.38-second quarter could satisfy Buick's efforts to be king of the strip.While the public enjoyed the thrills of the Stage 1 package, Buick quietly worked on the development of its even more powerful Stage 2. The extensive performance upgrades included special heads, an 11.0:1 compression ratio, a revised camshaft, a Holley 850 carburetor, an Edelbrock intake, and some Mickey Thompson headers. However, with the switch to unleaded fuel imminent, the package was never fitted to a car from the Buick factory. How Buick GS 455 The Stage 2 Stacks Up Against Its Rivals Mecum 1970 Muscle Car Engine Specs Comparison Hemmings, HagertyAcross the board, torque output is consistently above 400 lb-ft, but you'll find that Buick's GS 455 Stage 2 has a decided edge when it comes to power. Even if other manufacturers were similarly conservative in their ratings (the Mustang Mach 1 is believed to produce closer to 400 ponies), the Stage 2 was still several stables ahead of the competition – some sources report as much as 540 horsepower from the 455 cubic inch V8.Buick developed the Stage 2 package with Super Stock racing in mind, and the upgrades gave the car more than enough grunt to move down the strip with authority. For perspective, Hot Rod magazine managed a 13.44-second quarter 108.17 mph in a Chevelle equipped with the LS6 V8. Even with 3.55 gearing, the best that Car Craft could manage was a 13.12 at 107.01. Reported Buick Stage 2 Drag Strip Results Mecum Auctions Per Bangshift, early testing showed runs of 10.7 seconds at 123 mph Team Buick reports one owner running a 10.64-second quarter at 124.65 mph The GSX ran 11.7-second quarters, but the Jones-Benisek GS was reportedly a full second faster Official times are hard to come by, but there are multiple claims to the Buick's performance prowess. And all of them have one thing in common: the GS 455 running a sub-11-second quarter. Even budgeting for testing conditions and timing inaccuracies, there's no denying that the Buick would have handily beaten other muscle cars of the 70s if equipped with a Stage 2 kit from the factory. Your Chances Of Finding A Stage 2 Today MecumWith over 500 horsepower on tap and the ability to run sub-11-second quarter-miles, the Stage 2 had the potential to completely disrupt the muscle car segment. However, Buick higher-ups ultimately decided that it would be too much for the public, and the project was axed before any factory-equipped cars could be built and sold. Racers and connected customers could buy the kits as early as 1969, but it wasn't until 1972 that they became options at dealers. By that point, the malaise era was beginning to take effect, and Buick's GS was rated for a much less exciting 270 horsepower.As such, Buick only sold a very select number of Stage 2 packages. It's generally agreed that less than 100 examples left the factory, but some sources suggest that as few as 75 kits exist with the later-style Stage 2 heads. Regardless, they're as rare as hen's teeth – Buick club members have reportedly only managed to track down a few dozen sets. For this reason, you're better off looking at GS 455 Stage 1 prices before even embarking on your search for elusive Buicks.Mecum Auctions 1970 Buick GS 455 Stage 1 Values HagertyIf you have your heart set on a droptop experience, be prepared to pony up. By Hagerty's estimation, a 1970 GS 455 Convertible equipped with a Stage 1 package will run you nearly double a comparable Sport Coupe for all but the nicest examples. Still, you're doing well compared to a of the same year – a 'Good' condition LS5 is valued at $61,500, while an equivalent LS6 starts at $98,000. Convertible Chevelles will run you some $87,200 and $239,000, respectively.Classic.com's recent sales support Hagerty's valuation. As you'll find from the results below, the Buick GS 455 Stage 1 can prove to be a costly car at auction. Buick GS 455 Stage 1 Pricing (Classic.com) Mecum 1970 Buick Gran Sport 455 Average Sale Price (Not Stage 1 Exclusive): $71,977 Most recent coupe sale: $46,200 Most recent convertible sale: $192,500 That said, the featured hero car sold for some $77,000 at Mecum's Kissimmee, Florida auction in 2020, so Stage 2 components don't completely transform GS values. If anything, the bigger challenge is tracking down such a rare performance option.