Page 199 of GM Performance Parts 2006 Catalog by GM Parts Direct

Production-Based Bare Block (rear) Production-Based Bare Block (front) PRODUCTION-BASED BLOCKS The GM Performance Parts production-based blocks are the right choice for street car rebuilds or to start your own mild engine project. They come in the same dimensions that you are already familiar with and are produced to the high level of quality that GM is famous for. Remember, these are brand new castings that are machined to our exacting tolerances. These blocks are designed for street engines that demand good strength and a high level of durability. One of these blocks has siamesed cylinder walls 1 and both have four-bolt main caps 2 that are secured by Grade 8 bolts. Both blocks have a 9.800" deck height. These production-based blocks are a great foundation for your serious street car or drag car that makes between 350 and 500 horsepower. Production-Based Block Technical Notes: Can accept Mark IV, Gen V VI iron and aluminum cylinder heads Require Gen V or Gen VI design one-piece rear main seal oil pans 9.800" standard deck height Machined for hydraulic roller or flat tappets See chart on page 196 for complete specifications. 12561353 427/454 Bare Block Production type cast iron 4-bolt block 4.25" rough finished bore 4.31" max bore (non-siamese bore) Machined mechanical fuel pump pad 10237292 502 Gen VI Bare Block Production type cast iron 4-bolt block Siamesed cylinder walls 4.47" rough finished bore 4.500" max bore (siamese) Reinforced deck surfaces for better sealing Foundation of our 502 engine assemblies 1Siamesed cylinder walls have thicker cylinder wall material with no water between the bores. This allows for a bigger bore; a bigger bore allows for more cubic inches and more power! 2Four-bolt mains have more material and more fasteners holding the crank in the block (4 bolts per main instead of just 2). Fourbolt mains help maintain the integrity of the block when you drop the hammer! 197 Straight 4-Bolt Mains One-Piece Rear Main Seal

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