The classic Chevy Big-Block production engine wasintroduced in 1965. In the late 1980s, a new versionarrived, designed for marine and fuel-injected applications.The early-style engines are known as Mark IV Big-Blocks,while the later style is referred to as the Gen V (and GenVI) Big-Block. You can tell them at a glance by checking fora mechanical fuel pump mounting pad. If it has one, it's aMark IV. If there's no fuel pump pad, it's a Gen V block.

Despite the fuel pump mounting pad difference in theircastings, the cylinder blocks of the Mark IV and Gen V arebased on the same design architecture. There are severalother differences?particularly in the water jackets near thedeck surfaces?that make some Mark IV and Gen V partsincompatible, including crucial components such as thecylinder head gaskets.

Within the last few years, Chevrolet Performance revisedthe basic Big-Block architecture to commonize the Mark IVand Gen V, creating an all-new cylinder block casting thatcombines the features of both generations. It also incorporatessignificant updates and strength-enhancing features that makethe Big-Block a stronger engine foundation with provisions tosupport 21st-century performance.

Although the basic Big-Block architecture is revised,Chevrolet Performance continues to offer two versions,each differentiated by performance and displacementcapability. The Bowtie block continues to be the block ofmaximum performance. All of our crate engines use therevised Big-Block design.