Chevrolet Chevelle SS 1970 images

When GM lifted its ban on big-block engines in mid-size cars for 1970, Chevrolet answered by stuffing a 454 into the Chevelle — and one version of that engine actually outrated the Corvette. Only around 4,475 of the wildest LS6 examples were built. Here’s what made this one-year-only combination the high-water mark of the entire Chevelle lineup.

1970 Chevrolet Chevelle SS 396 CID V8 TH400 3-SpeedÂ automatic

MCF thanks Gateway Classic Cars for the images displayed here.

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For most of the 1960s, General Motors enforced a corporate rule capping engine size in mid-size cars, and everyone from Chevrolet engineers to eager buyers hated it. When that rule finally lifted for the 1970 model year, Chevrolet didn’t waste a single afternoon before dropping the biggest engine in its parts bin straight into the Chevelle, and the result became the high-water mark of the entire muscle car era. Buyers had two versions of that big engine to choose from, one mild and one absolutely unhinged, and only one of them earned bragging rights over the Corvette. That distinction alone tells you everything about what General Motors was willing to unleash once the leash finally came off. So what exactly made this particular Chevelle the one every other GM performance car got measured against?

The Engine GM Wasn’t Supposed to Build

Once the corporate ban on big-block engines in mid-size cars lifted, Chevrolet stretched its 427 cubic-inch big block into a 454, offered in two flavors: the milder LS5 and the race-bred LS6. The LS6 was a one-year-only option for the Chevelle, built with a solid-lifter camshaft, an 800-cfm Holley four-barrel on an aluminum intake, 11.25:1 compression, and a forged-steel bottom end, all combining for a factory rating of 450 horsepower and 500 lb-ft of torque.

Why It Beat the Corvette on Paper

The LS6 Chevelle stands alone in GM history as the only vehicle ever to carry a higher factory horsepower rating than the Corvette in the same model year, a fact that still surprises people who assume the Corvette was always the brand’s performance flagship. Only about 4,475 LS6 units were built for 1970, and clean, documented survivors now sit among the most valuable Chevelles of any year.

The Rest of the Lineup Buyers Could Choose

Not every 1970 Chevelle buyer wanted or could afford the LS6’s race-bred intensity, which is why Chevrolet kept the milder LS5 454 and a range of small-block options on the order sheet as well. The LS5 delivered a still-serious 360 horsepower in a more streetable, tractable package, while base V8 Chevelles offered buyers real performance without the compromises that came with a solid-lifter big block. That range of options is part of why 1970 Chevelles remain so collectible today — there’s a version for nearly every kind of enthusiast.

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