What does the Dodge Magnum 360 have in common with the GM LS engine family? In fact, what does a Magnum 360 (or smaller 5.2L 318) have in common with most every production small block?
The answer is that it responds very well to a cam upgrade.
The reason for this is not some magic inherent in the fuel-injected, Magnum engine design, but rather the use of such mild cam timing on factory applications. Since power production is but one of the many design criteria of a factory cam, engineers are not free reign to add a few extra horsepower just for good measure. Believe me, they know these motors much better than the aftermarket, and could easily up the power ante if given the opportunity, but the cam choice must not only make the desired power, but also produce the desired idle quality, fuel mileage, emissions, and drivability, to say nothing of traveling 100K, 200K, or even 300K (or more) miles without complaint.
Toss in the fact that motors like the Magnum offered plenty of displacement (more than Ford or Chevy), ample head flow (for the time), and even a decent induction system (Kegger!), and you have motor basically begging for a cam swap. The question now, how much does a mild cam upgrade actually improve a 360 Magnum?
Dodge Magnum Engine Initial Testing
To answer this question, I took Westech Performance up on an offer to use their Dodge 360 Magnum crate motor from Mopar Performance. Having sat idle for over 12 years, it was time the old 360 got some love. Though a crate motor, the 300-hp Mopar Performance 360 was basically a production (assembly line) Magnum equipped with a dual-plane (Mopar Performance) M1 intake. It was up to the user to supply the necessary carburetor, distributor, and exhaust.
Recent testing comparing this crate motor to a junkyard 360 Magnum produced (not surprisingly) identical power results between the two (when identically equipped).
For this test, the 360 Magnum was equipped with the MI dual-plane intake, a Quick Fuel 750 Brawler carburetor and (to get things started) a set of factory cast-iron exhaust manifolds. Before the cam upgrade, we wanted to test an internet theory that the larger-diameter outlets (and internal configuration) on the 1992 and 1993 factory manifolds offered a power gain over the smaller, later (1994+) manifolds. We then compared the two different factory manifolds to a set of long-tube headers.
Equipped with the smaller (1994+) stock manifolds, the 360 produced 291 hp and 390 lb.-ft. of torque. The larger manifolds added a couple of horsepower, with peaks of 294 hp and 394 lb.-ft. of torque.
The long tube headers offered the most power on the carbureted 360, with peaks of 301 hp and 403 lb.-ft. of torque. We suspect the differences would be even greater on a wilder combination, but obviously long tube headers offered the greatest gains, even on a near-stock Magnum.
Dodge Magnum Camshaft Selection
After the exhaust modifications, we turned our attention to the cam swap. Selecting a cam for any application is very important, as the cam determines the personality of the motor. The cam must also be matched to the remainder of the components, as they must be designed to work together in the desired rpm range. No sense in selecting a cam designed to make peak power at 7,000 rpm if the intake and head flow all limited power production to 5,500 rpm.
The same can be said for intended usage. The cam designed to enhance low-speed torque, or at least not lose low speed torque in the quest for some additional power through the rest of the rev range, will certainly be different than a cam designed for frequent trips to the strip!
The cam choice must also consider things like desired idle quality, fuel mileage, and choice of torque converter (as in, is a tighter converter necessary)?
Care must also be taken with valve springs, as most cam upgrades require a matching valve spring upgrade. The springs must not only allow the desired cam lift (with concern to coil bind and retainer to seal clearance), but also sufficient spring rate to allow for the extended rpm offered by the cam. Lucky for enthusiasts, the cam manufacturers often have spring recommendations to go with their cams. When it comes to camming your Ram, choose wisely!
Dyno Testing the Dodge Magnum Cam Swap
Knowing all of this, we selected a suitable cam for the 360 Magnum. With low-speed torque and a daily driver in mind, we chose a mild, but plenty powerful grind from Comp Cams.
Designed for computer-controller Magnum engines, the Xtreme Energy XR262HR cam offered .480 lift, a 212/218-degree duration split and a 114 degree LSA. The wide LSA ensured a friendly idle quality, while the added lift and duration all but guaranteed additional power. Comp offered milder and wilder grinds for looking for even more drivability or power.
We made short work of the cam swap, reusing the factory lifters. As luck would have it, sometime in the life of this crate motor (did we mention it had been sitting idle for about 13 years?), the springs had been upgraded. They offered not only 140 pound of seat pressure, but sufficient coil bind clearance for our .480 lift. Run with the stock cam and headers, the Magnum produced 301 hp and 403 lb.-ft. of torque.
After installation of the new Comp XR262HR cam, the peak numbers jumped to 350 hp (technically 349.8 hp) and 418 lb.-ft. of torque. The cam swap not only improved both peak horsepower (by 49 hp) and peak torque (by 15 lb.-ft.), but the cam offered power gains from 3,000 rpm on up. In truth, we step up a little more than we wanted on this Magnum application.
In typical go-for-the-glory fashion, we were more enticed by the big peak horsepower numbers than the usable power down low. For a daily driver, an even better choice might be the XR258HR which drops down 6 degrees of duration on both intake and exhaust, but it might be nice to see how close we can get to 400 hp with a few more mods like hand-ported and milled heads and a different intake manifold.