In 1970, Chevrolet increased the size of the Mark IV big block to 454 cubic inches, and released yet another legendary big-block engine. The LS-6 454 was certainly the most potent big block available to the average enthusiast. Most of the other “special” big blocks were built in very small runs, and in many cases the local Chevy dealer didn’t even know they existed. Everyone, however, knew about the LS-6. A forged steel crank spun in 4-bolt mains. Heavy-duty connecting rods featuring 7/16” bolts were connected to forged, domed pistons yielding an 11.25:1 compression ratio. Rectangular port cast-iron heads with 2.19” intake and 1.88” exhaust valves were topped with an aluminum intake and Holley carb. The intake used was a low-profile unit, which certainly cost some horsepower but allowed the engine to be installed in the Corvette with its very low hood line. The mechanical camshaft was the same piece used in the 396/375-horse and 427/435-horse engines. Power production of the LS-6 was 450-horsepower, which gives the beast the distinction of being the most powerful Chevrolet engine installed in a production model (at least according to factory ratings). Although initially earmarked for the Vette, the engine is actually most closely associated with the 1970 SS 454 Chevelle. A Super Sport Chevelle with the LS-6 is certainly thought of by Chevy fans as the ultimate muscle car, and it’s hard to argue with them.

The original plan for the Corvette in 1970 was to pick up where the 427 left off with the big-block. The L-88 427 would simply reappear as the LS-7. The fabled aluminum-head LS-7 almost made it into production. No factory built LS7 cars were ever sold to the public. However, the LS7 heads were available over the counter at GM dealers in '71 and '72. It was a kind of special situation in 1970 - from factory the Chevelle had more horsepower as the Corvette

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