Page 136 of GM Performance Parts 2006 Catalog by GM Parts Direct

NOTE: GM PERFORMANCE PARTS BOWTIE SPORTSMAN BLOCK This is the block to buy if you want to build a serious street car or if you want to head to the race track! The GM Performance Parts Bowtie Sportsman block has been the starting point for countless racing engines. These iron blocks are available in a variety of finish options to build almost any engine combination. Most of these blocks have siamesed cylinder walls 1 and four-bolt main caps 2 that are secured by Grade 8 bolts. All blocks in this family have a 9.025 deck height. The Bowtie Sportsman blocks are a great foundation for your serious street car, circle track, or drag car that makes between 350 and 500 horsepower. Bowtie blocks are called out by main journal sizes (i.e., 283, 350 or 400) and then by bore size (i.e., 283, 305, 350 or 400) if the bore is not standard to the main size. Example: #24502501 350 Main- 283 Bore size has standard 350 main journal sizes, however the bore is standard 283 size (for those of you old enough to remember 283s). Bowtie Sportsman Block Technical Notes: 2.00" O.D. cam bearings (1.867" I.D.) P/N 12370843, required at all five locations (except for block 10051183) 0.900" thick main bearing bulkheads, Grade 8 main bolts Priority main oiling system Standard 9.025"deck height Cylinder bores have a nominal wall thickness of 0.340" 0.225" minimum cylinder bore wall thickness at 4.155" bore (excluding P/N 10051181, 10051183, 10185047) Extra thick deck surfaces with blind-tapped head bolt holes for improved head gasket sealing Tall lifter bore blocks may require clearancing the top of lifter bores for use with some roller lifters Timing system clearance must be checked for interference Lifter valley oil scavenging boss behind cylinder #8 below bell housing flange is present, but not drilled tapped Oil dipstick holes are not drilled Use seal adapter P/N 10051118 to use 2-piece rear main crankshafts in 1-piece rear main blocks See chart on page 132 for complete specifications. Two-Bolt 350 Main Blocks Two-bolt main bearing caps are installed to simplify the installation of the heavy duty four-bolt steel main caps with splayed outer bolts. A. 10051183 350 Bowtie Block, 1-piece rear main seal Cast iron maximum effort block 2-bolt mains 3.980" rough bore 4.090" max bore (siamese cylinder bores) 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! Two-Bolt Main Block (front) Two-Bolt Main Block (rear) CHEVY SMALL-BLOCK V-8 134 Two-Bolt Rear Main (no seal adapter) Two-Bolt Main Block A A A A

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