Top 10 Reasons to Build GEN VI Based Chevrolet Big Blocks

Gen VI Chevy blockUnless you require a specific block casting for a numbers matching restoration project, there is no longer any reason to seek, build or hoard original Mark IV engine blocks. Newer GEN VI engines came only in trucks and blocks have become more available in wrecking yards. Chevrolet Performance offers all new blocks providing all the  improvements necessary for top performance in both street and racing applications. The following features make these blocks far more attractive than original style Mark IV blocks.

Gen VI Chevy blockTop 10 Reasons to Build Gen VI Big Blocks

1. Standard production 4-bolt mains
2. Priority main oiling
3. One-piece rear main seal
4. Thicker deck surfaces
5. Thicker cylinder walls
6. Revised coolant passages
7. Accepts all Mark series cylinder heads
8. Machined fuel pump pad
9. Revised oiling to allow for bigger cam bearings/cam lift
10. Set up for roller cams or flat tappet cams


  • Bowtie Sportsman versions have splayed bolt main caps
  • Choice of siamesed or open cylinder bores
  • Can be drilled for use with 10-bolt front timing cover
  • Auxiliary oil pressure line added to front of block
  • Racing-style oil filter cast feature with added oil pressure port
  •  Two bosses added for manual transmission clutch pivot (machined)
  • Additional material added around lifter bosses
  • Additional clearance added for roller timing chains


BBC Block specs
GEN VI blocks all have 4-bolt mains, priority main oiling and leak resistant 1-piece rear main seals. These cylinder cases have revised cylinders in either siamesed or open configuration and they provide thicker cylinder wall and deck surfaces for greater stability. They accept all common big block cylinder heads and they incorporate a fully machined fuel pump pad and provisions for either hydraulic or flat tappet lifters. Study the accompanying features to see how a GEN VI block can enhance your next big block build.