It’s all about the steel. The new World Products Merlin IV iron block is made from 35,000 psi high density cast iron alloy offering greater strength over their previous 30,000 psi iron and a huge upgrade over OEM stock grey iron castings. Company rep Jack McInnis pointed out some of the additional features of the new Chevy big block.

“There is an increased thickness in the cylinder bores for the Mervin IV block along with added material in the main webs,” McInnis adds. “With our 4.600 block option, there is .310-inch wall thickness.

Along with the standard big block Chevy 9.800- and 10.200-inch deck heights, additional options are also available at 9.500-, 9.850-,” and 10.250-inches.

McInnis explains, “This is a great set of options for better piston configuration where you can try to get a better stack-up of the rod pins and ring locations.”

The extra stud bosses for the upper inside of the head bolt application offer extra material inside the water jacket. This provides far greater overall strength.

McInnis mentions, “You can put 70-foot-pounds of torque on those bosses. That is something you couldn’t do before to benefit gasket clamping.”

The Merlin IV is available with a 2.120-inch big block Chevy cam journal and standard .842-inch lifter bores. An optional combination of a 2.283-inch cam journal for a 55mm babbitt cam mated with 904-inch lifter bores is also available.

“We added many instances of increased material throughout points of the block for strength,” McInnis explains. “But we maintained the same general overall weight balance related to previous blocks by reducing material specs in other areas such as the bellhousing where it doesn’t detract from strength.”

World Products has also has added a front oil feed for dry sump systems, and relocated the lifter oil feeds and restrictor provisions to the front of the block. The new block’s oiling system has revisions as well. It is still a “priority main” oil path design, but with the main galley feeds increased in size and a bigger feed from the oil filter pad.