Cam Your Ram: Part 1
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The Chevy guys seem to be getting all the press lately, but as good as the GM LS family is, it ain’t the only game in town. Just ask any diehard Ram truck owners and they will be quick to point out that only one manufacturer can claim ownership to the legendary Hemi name—and that’s Dodge. Definitely a blast from the past, the modern Hemi has proven itself a worthy successor to its legendary namesake. While the modern engine might be down on displacement compared to the 426, the missing cubes are more than offset with terabytes of technology. In addition to the fancy fuel injection, the modern Hemi can be blessed with Multiple Displacement Systems (MDS), Variable Camshaft Timing (VCT) or even Active Intake systems. Toss in the recent introduction of the larger 6.4L (392ci) version, and it’s very clear the Dodge boys have not forgotten how to make Hemi horsepower.
Like their GM counterparts, the Hemi engines (both 5.7L and 6.1L) were blessed with impressive cylinder heads. Even in stock trim, the intake ports on a set of 5.7L heads can flow better than 260 cfm. That is enough to support over 525 hp on the right (normally aspirated) application. The 6.1L heads flow even more, but both heads will respond to porting, with peak flow numbers as high as 360-370 cfm. The benefit to all this head flow is that it allowed Dodge to produce exceptional power without resorting to wild cam timing. On production engines, milder cam timing improves idle quality, drivability, and fuel mileage, but ultimately limits power production—especially at the top of the rev range. The impressive head flow offers a secondary benefit as well, this time to the owners of Hemi-powered Ram trucks (and cars). Having mild cam timing and (relatively) excessive head flow means the combination is just begging for a cam swap. It also means the power gains offered by even mild cam swaps can be substantial. Enter our boneyard brawler!
To illustrate the fact that Hemi engines respond very well to cam swaps, we decided to run a back-to-back test on the engine dyno. Before we could let the wrenches fly, we had to select a suitable test engine. While crate and performance Hemi engines abound from various sources, we decided that the best candidate would be a bone stock 5.7L. More specifically, a 5.7L pulled from the engine bay of a Dodge Ram truck circa 2006. Ours came from a local wrecking yard and while not quite as affordable as the comparable GM 5.3L offering, the 5.7L Hemi came complete with wiring harness, sensors, and full accessories (a complete take-out engine) for $1,700. Considerably more than the $550 usually paid for a 5.3L LS, but a good deal when you consider the 5.7L offered both more displacement and power compared to the smaller 5.3L from GM. The 5.7L also offered something not available from any LS engine: the HEMI name. How do you put a price on a legend?
Initially we tried to install a Meziere electric water pump on the Hemi, but found out the 5.7L did not share the 6.1L water pump configuration. Since we elected to remove the accessories for dyno use, we were forced to run pressurized dyno water through the engine block. Not a big deal, just more plumbing during the initial set-up. Another modification required for dyno use was the conversion of the drive-by-wire throttle body to manual operation. We removed the cover plate and welded up a manual throttle arm (see photo). The stock 5.7L injectors and coil packs were tuned using the FAST XFI/XIM management system. This allowed us to quickly dial in both the air/fuel and timing curves at wide open throttle, then quickly get to our cam swap. The final elements on our 40,000-mile engine included connecting the dedicated FAST Hemi wiring harness, treating the 40,000-mile engine to an oil change (Lucas 5W-30 synthetic & K&N oil filter) then hooking up the fuel line from our dyno regulator to the stock fuel rail. Hemi owners, we have ignition.
The first order of business was to establish a baseline by running the 5.7L Hemi engine with the stock cam. Rated by the factory at 345 hp and 375 lb-ft of torque, the boneyard brawler pumped out 370 hp and 407 lb-ft of torque. Torque production from the 5.7L exceeded 375 lb-ft from 3,200 rpm to 5,100 rpm, making for one sweet and effective torque curve. Why the difference between the factory rated and actual power outputs, you ask? Not that it makes a difference for our back-to-back test method, but the factory power rating was derived not from the wheels (as many have incorrectly claimed online), but from the flywheel in as-delivered trim. The as-delivered trim means with all accessories, full induction and exhaust systems in place (including cats) and running the factory tune at the specified coolant temperature. For our testing, we had more or less altered and/or optimized all of the variables. We removed the accessories, eliminated the induction and exhaust systems in front of the throttle body and behind the exhaust manifolds.
Lucky for us, the Dodge Hemi and LS engine also have another thing in common. Cam swaps in the Hemi are as easy as they are in the LS, meaning you don’t have to remove the lifters to perform a cam swap. This is a definite benefit, as lifter removal requires head removal, extensive work indeed. Instead, Dodge engineers figured out a way to capture the lifters in place using plastic lifter guides (again like the GM LS family). All you have to do is rotate the cam and the lifters are pushed up out of the way and then retained by the guides, allowing removal of the cam. Of course, this can only happen after removal of the front cover, cam gear, timing chain and guide. Prior to our cam swap, we rotated the engine until number one piston was at TDC. The cam sprocket featured a timing mark which (at #1 TDC) was located at the 12 o’clock position. The crank sprocket was positioned likewise, but was not visible without removal of the oil pump. For reference, the crank key way (which is visible) was located in the 2 o’clock position. After unbolting the front cover bolts (don’t forget those on the oil pan), we removed the cam gear and set the timing chain aside. This allowed access to the tensioner/cam retaining plate bolts (access to the lower one is a tad difficult-but possible without removal of the oil pump) and rotation of the stock cam.
Previous testing has illustrated that the Hemi responds very well to aggressive cam timing, but it is possible to over cam an engine, especially a daily driver. The ideal situation for a cam swap on a daily driver is to ensure the cam upgrade improves the power output through the entire rev range. Big cams can provide a ton of extra power at the top of the rev range (especially on a Hemi), but these same cams often sacrifice low-speed and mid-range torque for that high-rpm rush. The reality is that a Hemi spends much more of its life in the lower rev ranges, even in spirited driving. Hemi owners should take that into account when considering the cam specs for a cam swap. Combining this with the fact that this engine was equipped with Dodge’s Multiple Displacement System (MDS), we installed a mild cam from the Comp Cams catalog. The 260H-13 (pt#112-500-11) cam offered .522/.525 lift, a 208/212 duration at .050 and a 113-degree lobe separation angle. There were a few smaller cams available in the Tri-Power Xtreme series, but this 260H-13 cam was the smallest offering in the XFI series. By comparison, the stock Hemi cam offered near .470 lift, 196 degrees of duration and shared the 113-degree LSA.
The cam swap went off without a hitch, but we made sure to lube the new cam up thoroughly before installation. After reassembly, the engine fired up immediately, indicating that it was ready to run. The Comp Cam offered not only impressive power gains, but offered them through the entire rev range. Equipped with the 260H-13 cam, the 5.7L Hemi produced peak numbers of 401 hp and 427 lb-ft of torque compared to 370 hp and 407 lb-ft for the stock cam. Measured peak to peak, the cam swap netted an additional 31 hp and 20 lb-ft of torque, but elsewhere along the curve the gains were as high as 57 hp and 53 lb-ft of torque. Every bit as impressive was the fact that the mild Comp cam offered an additional 20 lb-ft of torque down at 2,500 rpm. Torque production with the new cam exceeded 400 lb-ft from 3,500 rpm to 5,300 rpm, or right where it can be put to serious use in a Ram truck. There are obviously wilder cams available, but it’s hard to argue with the extra 31 hp and 20 lb-ft of torque we got from camming our Ram. Check back with us next month as we take the 5.7L to the next performance level by adding a stroker short block, some ported heads, and more aggressive cam timing. For those serious gear-head, Ram truck owners, we will follow that up in part 3 with some boost.
PEAKS
STOCK CAM: 370hp @ 5,200rpm, 407lb-ft @ 4,400rpm
COMP CAM: 401hp @ 5,600rpm, 427lb-ft @ 4,500rpm
