All Aluminum Hemi Engine - The Sky's The Limit - Tech

If you're like us, when you hear the words "aluminum Hemi" your mind leaps to images of nitro-slurping funny cars and rail dragsters from the golden age of drag racing-engines with satin-finished blower cases, fuel injection "bug catcher" intakes and fuel lines the size of fire hoses.

A generation ago, such a combination would have made an untold amount of horsepower, but times change. Today, it's possible to have an aluminum Hemi crate engine that makes nearly 80 percent of the power of the old fuel-sipping blown Hemi engines, but now it could be naturally aspirated with a single four-barrel carburetor-and on pump gas.

So, yes, we're talking about a streetable, nearly 800-horsepower all-aluminum Hemi engine. If that sounds almost too good to be true, consider that the fully dressed engine weighs only about as much as fully dressed iron small-block combination (527 pounds in our dyno-test trim).

What's the catch, you ask? None, really, other than the fact that World Products isn't exactly giving them away. But if your street/strip machine is in need of a big injection of power and your checking account is still more or less intact in these troubling economic times, World's big-inch, big-power aluminum Hemi is the cure for the low-e.t. blues-or the fix for a street machine that needs a little more attention on Saturday's cruise night.

The classic 426-style Hemi flirted with extinction on more than one occasion during the past 30 years, but it was kept alive by determined and dedicated enthusiasts. World Products entered the Hemi world a couple of years ago when it entered into a partnership with Mopar Performance to cast new, iron cylinder blocks.

But while the iron block is exclusively a Mopar Performance item, World used its design work on the block and then cast an aluminum version that's all theirs (they've even got a hardcore graphite block for the serious race engine builder). Like the iron casting they manufacture for Mopar, the aluminum block carries a variety of improvements over the original 426 Street Hemi on which it's based-features designed to improve the block's overall strength and ability to support larger-displacement combinations. This includes a provision for an externally mounted oil pump to free up extra room inside the block for a longer-stroke crankshaft.

More importantly, the aluminum block weighs only 142 pounds. That's less than half of the iron version's approximate 300-pound weight. The project engine outlined in this story displaces a Grand Canyon-esque 572 cubic inches-achieved with a square, 4.500-inch bore and 4.500-inch stroke combination (the block will accommodate up to a 4.750-inch crank, for a total of 612 cubic inches).

Channeling air in sufficient quantity to support the 572-inch displacement is a set of Indy 426-1RA aluminum heads. They offer big, 251cc intake runners, and 2.400/1.940-inch valves that allow more than 500 cfm worth of airflow at 28 inches of water.

The raised-port design of the heads requires non-standard pushrods, measuring 10.47 inches long on the intake side and 11.45 inches on the exhaust side. The heads also wear Indy's rocker arms, consisting of 1.60-ratio rockers on the intake side and 1.55-ratio rockers on the exhaust side-all mounted on an adjustable shaft system.

The hydraulic roller camshaft delivers .381/.381-inch lift and .258/266 degrees of duration on a wide, 114-degree lobe separation angle. That may seem like a comparatively mild cam by non-Hemi standards, but it works very well at balancing the engine's displacement and airflow capability of the Indy heads. It was also selected to enhance streetability, as the wider centerline delivers a good idle quality while helping build upper-rpm power.