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World Merlin IV BBC Engine Block 4.600 Bore 10.200 TALL Deck



Product Information

Product TypeShipped Product
Number of reviews 0

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This block is fully machined and ready for prep work. Please read the complete ad before purchasing.

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We now use all of the Merlin IV blocks in all of our BBC engine builds. The Merlin block is light years ahead in overall construction as compared to any of the other blocks on the market. The main caps all have ARP hardware. Dimensional specs are spot on, and this has been an issue with other blocks we have used in the past. Many of the top engine builders, ourselves included, have found the New Merlin IV block to be superior to other blocks in numerous ways.

World Products has completely redesigned the famed Merlin Big Block Chevy casting, incorporating numerous improvements and new features to virtually every area of the block.

Designated the Merlin IV, this new block is offered in all popular sizes and deck heights and is sure to be a favorite among racers and professional engine builders.

New Merlin IV features include upgraded 35,000 psi iron alloy with added material in the main webs, cam tunnel, and cylinder walls for increased strength. Cylinder walls are nominally .300" thick on the thrust side at 4.600 bore. Material was then removed in non-affecting areas in order to maintain the original weight.

The block also has an increased volume priority main oiling system with a .500" main oil galley. A front oil feed for dry sump systems is incorporated with front oil cross-overs and restrictor provisions, which now utilize standard pipe plug restrictors. The main oil galley has been relocated so that blocks with a 60mm cam will not require bushed lifter bores.

This Merlin IV has a 55mm Babbitt cam journal and .904" lifters. Cam journals up to 2.480" or 60mm Babbitt and 1.062" lifter bores can be accommodated.

All deck heights are nominally .600" thick, feature blind head bolt holes, and use standard length bolts or studs. The inside head stud provisions have also been revised to add strength by extending the bosses below the deck thickness in the casting.

The new block features siamese cylinders. Nodular iron or billet steel 4-bolt main caps are standard and are stepped and dowelled register and utilize ARP fasteners.

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World Products blocks and heads are 100% American made and are subject to stringent quality assurance procedures to ensure superior quality and performance.


  • 2-Piece Rear Main Seal
  • 4.600 Finished Bore Ready to use, (other bore sizes available)
  • 10.200" Deck Height
  • Standard BBC Camshaft Bearing Journal
  • Standard BBC Lifter Bore
  • Nodular Iron Main Caps
  • High Density Cast Iron Construction
  • Priority Main Oiling
  • Front Oil Inlet and Restrictor Provision
  • Bores to 4.625" max
  • Cylinder Walls 0.290" at 4.600" Bore
  • Valley Accommodates OE Roller Lifters or Use +.300" Tall Aftermarket Lifters
  • Clearance for 4.375" Stroke - 10.200" Deck
  • Splayed 4-Bolt Main Caps with Dowels & Stepped Register, ARP Fasteners
  • Accepts Standard Big Block Chevy Components
  • Up to 60mm Babbit Cam Bearing Journals & .904" Lifters
  • OE-style Fuel Pump & Starter Mounts
  • Approximately 270 lbs
  • Rated to 1000+ Horsepower
  • Made In USA

Warranty: World Products warrants its products to be free from defects in materials and workmanship. No other warranties apply.

The World Products Merlin IV block is bored and decked to size with our new Centroid touch probe machine. Few machine shops have a machine of this accuracy.

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We also deck the blocks to an RA finish of approx. 15 or better. The decking procedure is also done by our Centroid CNC machine. We will deck this block to the exact specs you need.

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When we're finished decking the block, it is within approx. .001 accuracy from end to end. Many machine shops fail to catch this as the machinery they use does not allow for such accuracy.

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We then plate hone the block with our new Sunnen SV15 diamond hone machine. This is also a very advanced machine that hones the block with a finish unlike conventional machines.

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The final step is to clean the block in our high pressure block washer.

    • We are not responsible for collateral damage caused by the use of this product.

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