Chrysler 318 Hughes Engines Replacement

Making A Small Engine Big With A Little Help From The Supercharger Store And Hughes Engines

From the May, 2010 issue of Mopar Muscle

By Dave Young

Photography by Dave Young

We've all heard the term "There's no replacement for displacement" more often than we care to recall, and when comparing big and small engines with similar induction methods, the cliché typically holds true. There are exceptions to every rule, however, so when the guys at Hughes Engines and the Supercharger Store said they wanted to build a Chrysler 318 that would meet or exceed the horsepower and torque numbers of a normally aspirated stroker big-block, and further, the engine would idle nicely, produce enough manifold vacuum for power brakes, and run on pump gas, we had to follow along to see how close they could come to achieving these goals.

Of course we all know that building a normally-aspirated 318 that would out-power a stroker big-block would be an extremely difficult feat, resulting in an engine that would hardly be streetable and likely wouldn't idle well or run on pump fuel at all. So, to see the expected results, this build would require the benefit of forced induction. And while some of you envision cutting a hole in the hood for an unsightly supercharger, the truth is there are many options when it comes to forcing air into your Mopar engine, one of the least intrusive being a centrifugal supercharger like those manufactured by ProCharger.

Since centrifugal superchargers are small in size, can be located under the hood, and spun in conjunction with other accessories like the alternator and water pump, and are easy to intercool, a ProCharger D1SC supercharger with a water injection system from the Supercharger Store was picked for this project. The idea was to build a somewhat mild 318, and through a moderate and reliable level of boost, increase the engine's output to an incredible 650 horsepower and 600 lb/ft of torque, while not making a huge sacrifice in drivability or economy. To get started, Hughes Engines offered to build a 318 for the project that isn't too far from the typical small-blocks our readers have likely built for their cars.

After some searching, Dave Hughes found a 318 that would pass his stringent requirements for cylinder wall thickness, magnetic particle testing, and would handle a cooling system pressure test to 30 psi. Once these tests were finished, the block was treated to a complete cleaning, boring, squaring, and honing with torque plates, and the decks surfaced to be completely flat. An Eagle forged-crankshaft was utilized with Eagle H-beam connecting rods, and Diamond forged pistons with a custom 21cc dish and coated skirts were matched with Total Seal metric rings for an 8.5:1 compression ratio, and the entire rotating assembly was balanced. Since the Chrysler small-block has numerous oil system issues in stock form, Hughes also blueprinted the oil system for optimum performance, installed a 10-inch-deep Moroso pan to keep oil away from the rotating assembly, and used one of their main girdles for additional support and reduced crankcase windage.

Racing Head Service (RHS) provided a pair of their new "X" castings for the engine, which are a big improvement over stock cylinder heads. The RHS castings offer two versions, LA and Magnum, and the Magnum style heads were chosen for this engine. Once received, Hughes installed their swirl-polished, stainless steel 2.02-inch intake and 1.62-inch exhaust valves, and treated the heads to their proprietary multi-angle valve job and slight bowl blending, but no extensive porting. The heads were topped with Hughes Engine's new 1.65 ratio shaft-mounted roller rocker arms, which require no girdle since each pair of rockers is mounted on an individual shaft.

Choosing a camshaft for any engine should be a well-thought-out process, and a supercharged engine is no exception. While small displacement engines like the 318 normally respond to less lobe separation, shorter duration and higher lift camshafts, supercharged engines generally require a wider lobe separation and not so much lift and duration, making an engine that idles more smoothly with better low-end throttle response. Knowing these parameters, Dave installed one of Hughes Engines' HEH2332AL flat-tappet camshafts with a 113-degree lobe separation, 223-degrees intake and 232-degrees exhaust duration at .050-inch lift. The cam's lift numbers are .556-inch intake, and .589 exhaust lift at the valve with their 1.65 ratio rocker arms. With the pieces in place, the 318 was assembled, broken in, and inspected before being shipped to the Supercharger Store where it would be dyno'd first without, and then with the ProCharger-based Supercharger Store kit installed.