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Throwback Thursday: ’63 Impala Z11 427

By the early 60s, the era of tailfins and chrome had come to a close, and early 60s full-size Chevrolets featured cleaner, boxier lines and more modern-looking interiors. Under the hood, the Impala was available with anything from a straight-six to a big-block V8 for real performance in a big, heavy car.

By ’63, the problematic 348 V8 was gone and the big-block 409 was on its way out. Chevrolets were starting to see real competition at the tracks, however, and the Z-11 was the answer to the big-inch V8 cars coming from Ford, Dodge and Pontiac. Chevrolet took the 409 engine and bored it out to 427 cbic inches, along with special heads, valves and a new intake manifold topped by two 4-barrel Carter AFB carburetors.

The Z-11 was built for one thing and one thing only: racing. That meant it was a no-frills car that didn’t feature a radio, front sway bar, sound deadening or even a heater. To cut weight, the Z-11’s hood, fenders, bumpers, bumper brackets, grill mounts, fan shroud, hood support catch and more were all fabricated from aluminum, cutting about 300 lbs from its total weight (compared to a 409-powered Impala SS).

The 427 was a radical engine for its day, with a high lift/long duration cam, 13.5:1 compression, cowl-induction air cleaner, factory exhaust headers and many other aluminum parts. The result was an astonishing 430 horsepower (although some ratings indicated 480 horsepower).

Only 57 Z-11 Impalas were produced, and only about 7 are known to still be in existence, making them a kind of holy grail of Chevrolet muscle.