1963 Z11 Impala Race Bred

[Lee Stewart]

Perhaps the 427’s greatest improvement over the 409 was in the cylinder heads and intake manifold. Like the high-performance versions of the 409, the 427 used 2.19-inch intake and 1.72-inch exhaust valves, but the 427’s head castings were taller. This allowed the ports to be located higher for a straighter path from the intake into the combustion chamber. The dual-carburetor aluminum intake manifold was unique, too, and made in two pieces: the lower part served as the lifter valley cover and contained the water jackets, while the upper portion housed the raised intake runners. A pair of Carter AFBs topped the intake and drew air through a special cowl-induction inlet that fed the air cleaner.

Chevrolet reportedly made 57 Z-11s before GM pulled the plug on all of its racing programs. The 427 represents the pinnacle of W engine performance development and is legendary among enthusiasts of the breed today.