GM Performance Engine Block, Aluminum, 4-Bolt Mains, 4.240 in. Diameter Bore, 2-Piece Rear Main Seal, Chevy, ZL1 427, Each (PART #GMP-12370850)

These GM Performance ZL1 aluminum engine blocks feature an improved design of one of the rarest production engines ever built--the ZL1 aluminum big block used in 1969 Camaros and Corvettes. They feature a new casting made from 356-T6M aluminum alloy and have a 4.240 in. cast iron liner that can be bored to 4.300 in. The engine blocks allow for crankshafts with a maximum stroke of 4.375 in. and held in by 4-bolt splayed steel main caps.

Other highlights include:

  • Thread-in freeze plugs with O-ring seal
  • 2-piece rear main seal
  • Provisions for wet or dry sump oiling systems
  • Provision for mechanical fuel pumps
  • Compatible with all types of cylinder heads

SPECIFICATIONS
Brand GM Performance
Manufacturer's Part Number 12370850
Part Type Engines, Bare Blocks
Product Line GM Performance ZL1 Aluminum Engine Blocks
Main Journal Type Chevy 454
Engine Block Material Aluminum
Engine Block Style Aftermarket
Engine Block Deck Height Standard deck
Deck Height (in.) 9.800 in.
Cylinder Bore as Shipped 4.240 in.
Cylinder Bore Diameter 4.250 in.
Maximum Bore Diameter (in.) 4.300
Camshaft Location Standard
Main Bolt Style 4-bolt
Main Caps Included Yes
Main Cap Material Steel
Main Cap Fasteners Included Yes
Main Bearings Included No
Rear Main Seal Style 2-piece
Finished Cylinder Bores Yes
Raised Cam Location No
Cam Bearings Included No
Freeze Plugs Included Yes
Remanufactured No
Quantity Sold individually.

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