The timing set is closed off...
The timing set is closed off with a chrome cover.
The block's added material is packed around the cylinders, although the bore centers and deck height remain at the factory 4.800- and 10.725-inch specifications, respectively, so all factory-style cylinder heads and intake manifolds bolt on without a problem. The front and rear bulkheads are thicker than stock, for extra rigidity.
A new feature of the block is a change in the design of the oil pick-up tube mount, which was repositioned and features a new two-bolt flange that enables larger-stroke combinations. An adapter is provided for the original-style screw-in pick-up. Also, the oil circuit is improved; it feeds the rockers from both oil galleys, rather than the cam bearings.
World uses the same iron cylinder...
World uses the same iron cylinder heads offered by Mopar Performance. They have 170cc combustion chambers, 2.25-inch intake valves, and 1.94-inch exhaust valves. The compression ratio is about 10.25:1 with the domed pistons.
Additional updates and improvements over the original 426-style block include:
* Lifter bosses can accommodate 45- or 51-degree angles
* Provisions for Hemi or Wedge engine mounts
* Designed to accommodate all popular aftermarket starters
* Rear bellhousing flange accommodates Chrysler and GM transmission bolt patterns
In its day, the original 426 block was no featherweight; and because of the extra material in the casting, the new Hemi block is a bit heavier, tipping the scales at a pachyderm-appropriate 308 pounds. There's an aluminum version of the block that chops more than 160 pounds off the block's weight.
Inside the Crate Engine
The prototype 528-inch crate engine in our story arrives at its displacement with 4.500-inch bores and a 4.150-inch stroke. That's nearly a 25 percent displacement increase over the original 426 specifications, which used 4.250-inch bores and a 3.750-inch stroke.
Next up were the unique rocker...
Next up were the unique rocker arm assemblies, which use higher-than-stock 1.7 (intake) and 1.65 (exhaust) ratios to maximize airflow. Valve lash is extremely important with a Hemi engine in order to extract all of its performance potential.
Of course, all of the internals on World's engine are forged. They include Arias pistons-providing about 10.25:1 compression-pinned to 6.86-inch-long Eagle rods, all swinging on an Eagle 4340-forged internally balanced crankshaft. The camshaft is a hydraulic roller with 0.524/0.543-inch lift specs. Again, some of these specs, particularly the camshaft, will likely evolve when the production crate engines are finalized.
Doing the breathing for the prototype engine is a set of Mopar Performance Hemi heads. No porting or any other enhancements were made for the prototype engine-just an out-of-the-box evaluation to use as a starting point. A Mopar Performance dual-quad intake manifold straddles the heads, and it is topped with a pair of Holley four-barrels.
Despite the iconic and dramatic appearance of the engine, there is nothing exotic or overly custom about the combination. There's no compromising machine work, no use of "unobtainium" parts, and there's no special needs-such as 110-octane fuel, for example-to run it on the street. Indeed, it's the epitome of World Products' "build it big, but keep it simple" philosophy.
"We design engines for people to simply pull out of the crate, add their fuel and exhaust systems, and turn the key," said Mitchell. "A simple combination gives the owner less to worry about and ultimately makes the driving experience with his or her car more enjoyable. All the elements are available to us to make that happen with the Hemi."
Mitchell says the 650-horse prototype engine is only the beginning. "We're really excited about the possibilities the new Hemi block gives us," he said. "We're just getting started with it."
 A traditional dual-quad intake...  A traditional dual-quad intake manifold is used on the prototype engine, with a pair of Holley 4150-type carburetors. Like the other aftermarket components on the engine, the carbs are straight out of the box, with no modifications or tuning. That will likely differ on production crate engines, as World Products is known for building its own carbs to suit the necessary air/fuel needs of its engines. |  The ignition system is finished...  The ignition system is finished off with the plugs and wires. The angled, front-driven distributor is an instantly recognizable attribute of the classic Street Hemi. |  With the heads and valvetrain...  With the heads and valvetrain components installed, the iconic Hemi valve covers, from Mopar Performance, were next bolted on the engine. |
 An electronic distributor...  An electronic distributor was next inserted in the engine. It will connect to an MSD ignition box. This gives the engine much better performance and improved reliability over the original-style ignition system. |  A polished damper completes...  A polished damper completes the Hemi buildup. It matches the completeness of any of World's other crate engines. |  The aluminum Hemi block shaves...  The aluminum Hemi block shaves 166 pounds off the weight off the iron version, while adding incalculable exoticness to an engine compartment. |
 Cross-valley ribs are added...  Cross-valley ribs are added to the aluminum block to bolster its resistance to twisting and enhance overall strength. |  Here's a restored example...  Here's a restored example of a Chrysler FirePower V-8 that was found in vehicles like the original Letter Series models. This dual-carb exampled is characteristic of the '57 300C. |  A cutaway model on display...  A cutaway model on display at the Walter P. Chrysler Museum shows the dramatic domed combustion chamber, opposed valves, and central spark plug design of the first-generation Hemi. |