Mark IV Family ZL1 Chevy Engine - History Of The Big-Block Chevy

The legend began on the high banks of Daytona in February of 1963. A handful of Chevrolets arrived for the Daytona 500 with something mysterious under the hood. While Ford and Chrysler expected to compete against Chevrolet's venerable W head 409, the Bow Tie guys had a big surprise waiting for them. As Junior Johnson's Chevy thundered around the track at speeds in excess of 160 mph, every soul in the paddock, pits, and stands knew that was no W block. Hot on Junior's heels was Johnny Rutherford, in another Chevy. The Chevrolets of Ray Fox, Smokey Yunick, and Bubber Farr all ran with power unmatched by the 409, and Ford and Chrysler cried foul. [Tiny Lund eventually won the race in a Ford. In fact, the top five finishers were Fords. The highest finishing "mystery motor" was Johnny Rutherford, who finished Ninth, four laps down.-ed.] What was this mystery motor Chevrolet was running?

Inside Chevrolet Engineering it was called the Mark II, a 427ci V-8 that shared no bloodline with the 409, dubbed Mark I. The word "Mark" is derived from the European tradition, which uses it to designate succeeding phases of a design. Instead, this was a totally new design, beginning in the summer of 1962, when Chevrolet Engineering's Dick Keinath started work on a replacement for the W block. Dick used the same bore centers (4.84 inches) as the W block, so to differentiate the engines in the minds of those working on both, the planned successor was dubbed Mark II. It was this big-bore, short-stroke 427 powerhouse that tore up Daytona's banks.

The Mark III was a 1963 design study similar to the Mark II, but featuring a bigger bore center. None were actually produced, though, since it required too much tooling money at the Tonawanda engine plant to change bore centers. The Mark IV went into production in 1965, displacing 396 ci. Mark IVs were subsequently made in versions of 427 and 454 cid; deck heights were 9.80 inches.

What was kept under wraps at Daytona in 1963-and all through the development process-was the cylinder head design. Fewer than 50 of these engines were cast before GM slipped out of racing in January of 1963. The large-diameter valves were canted, causing them to stick out at odd angles, thus leading to the engine's nickname: Porcupine.

From 1965 until it was discontinued in 1974, the Mark IV big-block was produced in a variety of horsepower configurations. It served duty in everything from mundane station wagons with trailer packages to pavement-melting, steroid-swilling Chevys ruling the streets and the drags.

Even after they were discontinued, the Chevy big-block continued on as the GEN II crate motor powering today's drag cars, street rods, and hottest street machines. And like all great engines, the Chevy big-block will be around for generations to come.

1965 - 1974 Chevrolet Mark IV EngineSpecifications