The LS6 Chevelle became available as rival automakers offered a 400-plus cubic-inch engine in their intermediate-body style cars. GM reluctantly held the line, restricting displacement to 400 CID in all its mid-size cars except for the Chevrolet Corvette. Finally, giving way to requests from eager fans, in 1970 GM was intent on no longer ceding ground. Pontiac, Oldsmobile, and Buick responded with 455 CID engines from their full-size passenger cars, while Chevrolet introduced the 454 CI LS6, constructed with a forged steel crank and rods, forged aluminum pop-up pistons, a sold-lifter cam, and a single Holley 4-barrel carburetor on an aluminum high-rise intake manifold. Its 450 HP and 500-lb-ft of torque made it the highest of any production engine Chevrolet had ever built to that point in history. It would retain this title until the 2006 Corvette Z06 which had 505 horsepower.

Exterior changes for the 1970 Chevelle included several to the front-end treatment, including a slotless front bumper that housed rectangular parking lamps directly before the headlights. It had a split grille flanked on either side by dual circular headlights. The front fender's swept-back appearance was gone, and a new upper line ran from above the headlight level to the rear of the vehicle, above the rear bumper.

All 1970 Chevelles were given an improved full coil suspension.