As announced at this year’s PRI Show, July 2017 will usher in two new big-block Chevy’s at World Products. These products are so new that only the late-model 8.1L BBC was actually present in Indy. The Merlin IV, however, is right behind the 8.1L in its development phase. The prototype block had already been cast, but not machined in time to make the show.
The general idea behind the 8.1 Liter Big-Block Chevy (PN 018100) from World Products was to provide a direct replacement for the discontinued factory block that came in full-size trucks starting in 2001, which was also very popular in the marine industry. Like its OE predecessor, it is a cast iron block with a 10.200-inch deck height. It comes with a 4.245-inch bore and nodular iron main caps. The new 8.1L does boast improved oiling, but its best attribute is its compatibility with stock components such as the oil filter, oil cooler, accessory mounts, and crank sensor. Remember the 8.1L used an LS style EFI system, which is what has made it so popular. Though it accepts factory iron heads, World Products plans to release a CNC ported head to go with it.
“Like all our blocks, it is semi-finished. The engine builder will final hone it, hone the lifter to fit, and (in this case) that is about all. The deck is finished,” said Jack McInnis, who is in charge of marketing for World, Erson Cams and PBM. “You have to do it that way because everybody’s ring package and lifters have different tolerances, so there is no one spec. Everything is different.” And, in case you are wondering, all of World’s blocks are cast in a modern, ISO-certified U.S. foundry.
The Merlin IV, on the other hand, is the latest evolution of the Merlin design – a full aftermarket block capable of handling substantial power. While it is also a cast iron block, World offers 9.500-, .9850-, 10.200- and 10.250-inch deck heights with clearance for stroker cranks. The Merlin IV also has extra thick cylinder walls for stability and better ring seal. At a bore size of 4.600 inches they are still .290-inch thick. The deck itself is thicker as well, which allows for better gasket clamping with the help of improved bosses for the head studs. The block is made from a special high-density iron alloy with splayed 4-bolt main caps in nodular or billet. The main web structures are strengthened, and water jackets are expanded.
“We’ve increased the oil delivery. It uses a priority main oiling system, but we’ve increased the passages to take restriction out and get more volume,” Jack added. “We’ve moved the restrictor provisions to the front of the block. In the old Merlin, it took special oil restrictors with access in the back. Now it is a pipe plug like anything else, so we’ve simplified that. We make them off the shelf with an upgrade to a 55mm cam and .904 lifters. It will accommodate a 60mm Babbit cam and up to 1.060 lifters.”
They say there is no replacement for displacement, and thankfully the Merlin IV offers that in spades. The Siamese bores will go to 4.625 inches (4.245, 4.495 or 4.595 are standard), and the block is clearance for 4.750-inch stroke on the taller deck heights – 4.375-inch with the 9.850-inch deck. Do some quick math, and that comes out to a max of around 588 cubic inches with the shorter deck and 638 with the tall decks. The front oil feed is perfect for dry sumps to control oiling with that massive stroke, too.
Stay tuned for more on these hot aftermarket blocks from World Products.