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Cast Iron BBC 8.1 Liter

World Products new 8.1 liter block is a direct replacement style with all the OE fitments and accessory mounts. The 8.1 engine is no longer in production and until now there have been no direct replacement blocks available. These engines are common in trucks, motor homes, marine and industrial applications.

Like all World's blocks and heads, The 8.1 liter is American made. World's new digital inspection equipment and quality verification procedures ensure dimensional accuracy and mean you can be assured of total quality and superior performance



  • Block Applications: The Merlin 8.1 blocks are designed to be a replacement for the GM 8.1 Vortec.
  • Block Material: High density cast iron
  • Deck Height: 10.245"
  • Deck Thickness: Approximately .600"
  • Cam Bearings: The Merlin 8.1 uses stock BBC cam bearings CH12 
  • Head Gaskets:Uses stock GM 8.1 Vortec head gasket
  • Main Bearings: Standard 8.1 Vortec
  • Main Caps: Nodular iron 4 bolt style
  • Lifter Bores: GM 8.1 Vortec lifters and retainer tray 
  • Maximum Bore: Part# 018100/4.310", Part# 018101 and 018102/4.625"
  • Water Jackets: Expanded for better cooling
  • Oil pump drive: Stock 8.1
  • Oil System Features: Redesigned, all stock 8.1 oil coolers will work
  • Filtration: Stock
  • Oil Pan: Stock
  • Stroke Clearance: 4.750" w/ Steel rods
  • Camshaft Location: Stock
  • Starter: Stock
  • Motor Mounts: Stock
  • Head Bolt Holes: Designed for stock GM 8.1 Vortec head bolts

Definitions and Dimensions:

Bare Blocks: Due to a vast difference of opinion among professional builders regarding specifications and procedures, all blocks, when purchased bare, are finished within GM +/- tolerances. Merlin blocks are supplied with the following specs:

Deck Heights: 10.245 +- .005

Cylinder Bore: 4.245, 4.495, 4.595 +/- .001.

Main Journals: 2.9375 +/- .0005. .8437 +/- .0005. 4.750.

Lifter Bores: .8437 +/-.0005"

It is the responsibility of the engine builder to finish the block to his or the end user’s preferences. MERLIN 8.1: Freeze plugs, dowel pins, oil galley plugs and cam bearings are not included or installed.