350 Main, 400 Bore Bowtie Sportsman Block


  • 350 main, 400 bore Bowtie Sportsman block
  • 1-piece rear main seal
  • 4-bolt nodular mains
  • 4.117″ finished bore; 4.155″ max bore


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350 Main, 400 Bore Bowtie Sportsman Block

P/N 12480175

  • One-piece rear main seal
  • CNC-machined cast-iron competition block
  • +/-0.005″ machining tolerances
  • 4-bolt nodular mains, splayed caps on center 3 mains
  • 4.117″ finished bore
  • 4.155″ max bore (siamesed cylinder bores)
  • Tall lifter bores
  • Comes with rear seal adapter

350 Main, 400 Bore Bowtie Sportsman Block

1-Piece Rear Main Seal

12480175 Chevrolet Cylinder Block

Step up to serious racing performance when you choose a Chevrolet Performance Block. These iron blocks provide a rock-solid foundation for any application in the 350-500-horsepower range, be it drag strip, circle track or high-performance project vehicle. These highly versatile blocks are available in a variety of finish options that enable maximum flexibility for building a wide range of engine combos. Most of the blocks have siamesed cylinder walls and 4-bolt main caps that are secured with Grade-8 bolts. Chevrolet Performance Bowtie Sportsman Blocks have 9.025-inch deck heights.

Bowtie Sportsman Block Technical Notes:

ユ Standard 9.025-inch deck height
ユ Nominal cylinder wall thickness is 0.340-inch
ユ Minimum cylinder wall bore thickness on 4.155-inch bore is 0.225-inches (excluding P/N 10051181, 10051183, and 10185047)
ユ Extra-thick deck surfaces have blind-tapped bolt holes for improved head gasket sealing
ユ Priority main oiling system
ユ Main bearing bulkheads are 0.900-inch thick and use Grade-8 bolts
ユ All five cam bearing locations require 2.000-inch O.D. (1.867-inch I.D.) bearings P/N 12370843 (except block P/N 10051183)
ユ Tall lifter bore blocks may require clearancing the top of the lifter bores for some roller lifters
ユ Lifter valley oil scavenging boss below bell housing flange is present, but not drilled and tapped
ユ Oil dipstick holes are not drilled
ユ Timing system clearance must be checked

Notes: Siamesed 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!

4-bolt mains have more material and more fasteners holding the crank in the block (4-bolts per main instead of just 2). 4-bolt mains help maintain the integrity of the block when you drop the hammer!

Prop65WARNING: These auto parts can expose you to chemicals including phthalates and lead. Installing or using these parts can expose you to other parts containing these chemicals and to engine exhaust, which are known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to