Without a doubt, looking back at the last three decades, the biggest development to come out of Chrysler was the introduction of the modern Hemi in 2003. Up until then, Mopar performance fans had to look backward and revel in the past glory of the old-school muscle engines: 340 small-blocks, 383, 426, and 440 big-block wedges, and of course, the legendary Hemi of old. If a Mopar fan wanted something to be proud of in the period between then and now, about the only bright spot was the Viper program-unless you wish to count those pesky turbo fours or turbo Mitsus. Yeah, not much there for a meat-and-potatoes Mopar man. The Hemi's triumphant return marked a seminal moment in Chrysler's performance evolution, and for good reason.
Preceding the Hemi, traditional V-8 power relied upon the updated and rehashed small-block with the Magnum series of engines-nothing here but good old 318 and 360 motors with roots going back to 1964 with the 273; the Magnums were an anachronism in the modern world. The new Hemi pulled the stops on technology, with the crowning touch being those allimportant Hemi heads. The older series of LA and Magnum small-blocks were limited by production cylinder heads hamstrung by small cross-sectional area, pushrod constriction, and ports that flow just about 200 cfm. The Hemi features wide-open ports, and even in the stock configuration, the Hemi offers flow approaching 270 cfm. In short, it's the perfect engine for a Mopar swap. With the old small-block, it would take a well-ported set of aftermarket heads to get to where the Hemi is stock, and that's not to mention the advantage of the Hemi's unconstricted port design, which pushes torque production up as rpm climbs. Getting serious port in an old LA small-block requires custom heads and heavy pushrod offsets. The Hemi comes from the factory with the ports for power.
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All this comparing and contrasting begs the question: Why build an old small-block when the Hemi has the goods? Really, a factory-stock 5.7 will put the hurt on a modestly built streetperformance LA or Magnum smallblock, and the output can rival a fairly serious effort on the older engine with a few mods to the Hemi. The answer seems to be that most Mopar guys would rather build on the old mill than deal with the wiring, computers, sensors, and EFI plumbing that come with the new engine. Even though the new Hemi has more power potential and used engines are becoming plentiful, the hassle of even thinking about making one of these modern engines run in an older car is turnoff enough.
What's the solution? Well, if all the troublesome installation issues are ironed out ahead of time, the Hemi swap becomes a sweet deal. This is where XV Motorsports comes in. First, the guys at XV looked at the injection question. Compared to bolting on a carb, working out a fuel-injection system is undeniably much more involved. For a majority of vintage Mopar fans, bolting on a carb and hooking up the fuel line is infinitely preferable to plumbing an EFI fuel system, with attendant wiring, regulators, pumps, and lines. Since the modern Hemi is throttle-by-wire, by the time all the EFI fuel system equipment and throttle body is tallied up, it is easy to be more invested in the support system than in the engine itself. A fat Holley sitting up center stage just looks right, while a aping throttle body up front seems all too wrong to traditionalists.
A difficulty in designing an effective manifold for the new-style Hemi is mating the verti
XV designed and cast a traditionalstyle, single-plane, four-barrel intake, making the swap to a carb a bolt-on. The manifold accepts a standard Holley 4150 carb in the conventional location. One of the design criteria was to retain a moderate overall height while maintaining a good transition in mating to the vertical intake ports of the Hemi heads. A shallow plenum and raised runners compared to other intakes on the market helped XV achieve this goal. This allows excellent hood clearance and compatibility with traditional Mopar scoops, air cleaners, and cold-air induction packages. There is no way to do that with a forward-facing throttle body. To up the ante further, XV can supply the carburetor already jetted and alibrated for the Hemi in various states of tune, from the base stock engine to XV's bigger cam packages delivering either a rated 400 or 420 hp.
The fuel system is just one side of the double-edged sword of installing a latemodel engine in a retrofit application. The other consideration is the ignition. If the fuel system seems problematic, the ignition and attendant wiring is enough to stop a Hemi swapper cold. With no distributor and 16 spark plugs, lighting the fire on a new Hemi presents a whole new set of questions. As with the induction solution, the idea at XV is to simplify the system for the end-user. Here, there's no way around a black box and wiring, but the ignition controller from XV simply plugs in where needed, and comes programmed and ready to run. With all the harness connections pre-terminated, solving the ignition requirement is simply a matter of mounting the box, plugging in the connections, and completing a twowire ground and power hookup. This ignition control unit comes calibrated with an ignition curve to match the engine package, though it is programmable by the end-user, or it can be reprogrammed by XV if further engine upgrades are performed.
A wide, shallow plenum gives space for an effective "waterfall" into the runner, helping e
On The Dyno
So what is the easy power potential of the 5.7 Hemi? Some dyno time gave us an opportunity to investigate what these engines can do, and gave us the chance to see the XV equipment in operation. Our baseline combination was nothing more than a bone-stock 5.7 Hemi, the same package you'll find in your local salvage yard or core supplier. (We priced a practically new salvage unit from Street & Performance at $2,500, which is the cost benchmark in our "Where The Money Went" sidebar.) Just like a guy slinging one of these mills into an old Duster, we pulled the factory intake and bolted on the XV four-barrel intake manifold. No issues here; the swap comes down to a few bolts. Next, an XV-calibrated 650-cfm vacuum- secondary Holley carb was stacked on top, and we had an engine with the familiar look we know and love.
The crew at Westech Performance Group mounted the engine to thei SuperFlow 901 dyno, bolted on a set of dyno headers, and our next job was the ignition. Our Hemi was an earlier (pre- 2006) version with the crossover waste spark system, which fires the second plug on the exhaust stroke for emissions purposes. XV's kit comes with the required short spark plug wire, which connects the coil pack to the second plug of the same cylinder, firing both plugs simultaneously. We pulled the XV harness and controller from the pack, and it plugged right into the Hemi just as claimed, only requiring an additional ground and switched ignition connection. Hooking up this system makes the old Mopar electronic ignition look complicated. With that, we were assured that the engine was ready to run, and it was. Too easy.
With everything already precalibrated, there was nothing left to do but warm up the engine and pull the throttle handle for our power numbers. With he totally stock engine running through a set of headers and the XV intake, carb, and ignition, we were shocked by just how docile and smooth the engine sounded and ran. With the OEM cam, the stock idle was in sharp contrast to the formidable power we found. Peak power came in at 371 hp at 5,800-5,900 rpm, while peak torque was recorded at 366 lb-ft at 4,800 rpm. It just goes to show the power potential in those new Hemi heads; these kinds of numbers would require a fairly well-built oldstyle 360, with a fair bit of cam chop to get there.
Part of the philosophy at XV is to take the guesswork out of a custom engine installation.
Swapping the factory "barrel" intake manifold and drive-by-wire throttle body for the XV c
XV's goal is to get the legwork done ahead of time, saving the end-user the hassle of dial
With the new Hemi, the oil fill is through the intake manifold and into a passage in the c
One of the peculiarities of the new Hemi is the dual plug arrangement. With the XV setup,
A crankcase vent provision is found on the opposite bank. We vented it open to the atmosph
On the dyno, the Hemi had a chance to show its potential. Even in all-stock form with just
Upgrades to the basic XV kit include the cam and valvespring kits in Stage II and Stage II
In addition to the cam, the Stage II and III packages include a valvespring upgrade. A spe
Keep in mind that our power numbers were created with the long-block in dead-stock form, i
Although the 5.7 Hemi features a cast crank, powdered metal rods, and hypereutectic piston
With nearly square ports and no pushrod intrusion, the Hemi intake ports are very efficien