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!
1. Our 5.7L Hemi test engine (circa 2006) came complete from a local wrecking yard for the
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.
2. Other items we elected to replace were the factory truck exhaust manifolds.
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.
3. The truck manifolds were replaced by a set of SRT8 manifolds. Not quite on par with the
4. The drive-by-wire throttle body was converted to manual operation by welding an extensi
5. 5.7L Hemis equipped with MDS lifters must run the MDS solenoids. Non MDS engines will u