During the last few years, the talk of new Hemi engines has typically referred to the third-generation units used in Chrysler's late-model products, such as Charger, 300C, and Ram. With the advent of stand-alone controller kits, we've seen more than a few popped in street rods-the most notable example being the SR-392 roadster, which was introduced last fall at the SEMA show.
For many rodders, however, real Hemi engines are the first-generation 331/354/392 mills or the aircraft carrier-sized 426 Street Hemi of the '60s and early '70s. The first-generation engines are long gone from the production scene, but the basic 426 Hemi has lived on for years in aftermarket form. Heads and other engine components sustained enthusiasts' needs, but no new Hemi blocks had been poured for quite a while.
The new casting of the vintage...
The new casting of the vintage 426 Hemi cylinder block is available from Mopar Performance. It is manufactured by World Products, who updated the design to accommodate contemporary desires for larger-displacement combinations and to improve oiling. World uses this block for its line of crate engines.
That changed recently with the introduction of a new Street Hemi block from Mopar Performance. It was designed through a partnership with World Products to be stronger than the previous example and support larger displacement. World Products manufactures the new Hemi block and Mopar Performance sells it, but World Products also uses the Hemi block as a foundation of an upcoming series of crate engines, short block assemblies, and so on.
The thought of new Hemi tech raises our pulse, so we jumped at the chance to check out the innards of a street-intended crate engine package that World Products is developing. Ours was an early glimpse of what was pretty much the first Hemi engine built by World Products. So, the caveat is the regular-production crates packages may vary slightly from what is shown in this story, but World's founder, Bill Mitchell, told us that, apart from some minor details, the engine is very representative of the final product.
To support large-displacement...
To support large-displacement combinations with the requisite strength, the Hemi block is cast with more material in strategic locations, such as around the cylinders. The maximum safe bore diameter is 4.600 inches. With the capability of supporting a 4.750-inch stroke, the Hemi has the capacity for 632 ci.
The basics include a 528-inch displacement, Mopar Performance Hemi heads, a 0.524/0.543-lift cam, and a pair of Holley four-barrel carbs. Naturally, our first question after gazing upon the gorgeous, dual-quad pachyderm was, "How much power did it make?"
Unfortunately, the answer was, "We don't know yet." It wasn't that the World Products folks weren't willing to share their data, but they were hung up on one thing: a global shortage of Hemi rocker arms. At the time of our photo session at World's Ronkonkoma, New York, facility, the engine was missing a couple of arms for one of the heads, so the backorder on the crucial valvetrain parts prevented us from participating in a dyno-test session.
But, Mitchell has been developing engines for a long, long time. His educated estimate on the combination's output is around 650 hp and 675 lb-ft of torque.
"We tend to estimate a bit on the conservative side," he told us. "But, given the components used in the engine and the airflow capability, that's probably a good idea of the power capability."
The internal oil pick-up location...
The internal oil pick-up location was moved and redesigned with a two-bolt flange. This enables longer-stroke crankshafts to be used without resorting to an external oil pick-up.
And, while 650 naturally aspirated horsepower is a crowning achievement in all regards, Mitchell pointed out the new Hemi block is designed to support larger displacements-more than 600 ci-so the potential of truly astounding power is only a few more cubic inches away. Of course, 6-71 and 8-71 blowers atop Hemis were so ubiquitous in the '60s and '70s that you'd have thought Chrysler offered them as over-the-counter accessories. We'd love to see what a healthy huffer with a vintage-looking Hilborn injection system would do for this engine.
New Hemi Block Details
At a glance, the new Hemi block looks virtually identical to vintage 426 Street Hemi cases. A closer inspection reveals more material in the casting, shoring up the block's strength and laying the foundation for big-cube combinations on the order of 600 ci or more. The block is available with 4.250-, 4.500-, and 4.600-inch bore diameters and can except a crank with as much as a 4.750-inch stroke (as along as an external oil pickup is used), giving a maximum displacement of a whopping 632 ci.
 The front and rear bulkhead...  The front and rear bulkhead rails are thicker than the original Street Hemi block, providing increased resistance to twisting. The front of the Hemi block also has a provision for an external oil-pump pick-up, which allows for a maximum-stroke crankshaft. |  Building the prototype crate...  Building the prototype crate engine started with the installation of an internally balanced Eagle 4340-forged steel crankshaft that provides a 4.150-inch stroke. |  The piston/rod combo consists...  The piston/rod combo consists of Eagle H-beam-style forged rods measuring 6.860 inches in length, full-floating wrist pins, and forged aluminum pistons from Arias. The pistons have a 65cc dome and a pin height of 1.785 inches. |
 The piston assemblies are...  The piston assemblies are connected to the Eagle crankshaft and torqued to spec. |  This shot shows the mountainous...  This shot shows the mountainous Hemi piston dome rising out of the block at top dead center. Just imagine squeezing up into that hemispherical combustion chamber. |  The internal oil pick-up was...  The internal oil pick-up was used on this 528-inch engine combination. As displacement crowds the 600ci level, an external oil pump is required to allow for the stroke. |
 An off-the-shelf oil pan was...  An off-the-shelf oil pan was bolted to the bottom of the Hemi block. The deep sump will likely cause installation issues for many street rodders. A custom pan will probably be needed for most rods. |  Camshaft selection for this...  Camshaft selection for this test engine fell to a hydraulic roller with 0.524/0.543 lift specs. That's certainly a fair amount of lift, but it is commensurate with the engine airflow capability and enables a very streetable idle quality. It was installed straight up. |  Connecting the camshaft and...  Connecting the camshaft and crankshaft is a true roller, double-row timing set. |