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Blocks and Components
A Better Big-Block
The classic Chevy Big-Block production engine was introduced in 1965. In the late 1980s, a new version arrived, 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 Gen VI) Big-Block. You can tell them at a glance by checking for a mechanical fuel pump mounting pad. If it has one, it’s a
Mark IV. If there’s no fuel pump pad, it’s a Gen V block. Despite the fuel pump mounting pad difference in their castings, the cylinder blocks of the Mark IV and Gen V are based on the same design architecture. There are several other differences—particularly in the water jackets near the deck surfaces—that make some Mark IV and Gen V parts incompatible, including crucial components such as the cylinder head gaskets. Within the last few years, Chevrolet Performance revised the basic Big-Block architecture to commonize the Mark IV and Gen V, creating an all-new cylinder block casting that combines the features of both generations. It also incorporates significant updates and strength-enhancing features that make the Big-Block a stronger engine foundation with provisions to support 21st-century performance. Although the basic Big-Block architecture is revised, Chevrolet Performance continues to offer two versions, each differentiated by performance and displacement capability. The Bowtie block continues to be the block of maximum performance. All of our crate engines use the revised Big-Block design.