For this junkyard turbo article, we decided to serve up a little bit of everything, starting with bolt-on boost to an otherwise stock Hemi motor. In our case, that stock motor was a '06 Hemi 5.7 from Dodge. Sporting the most recognizable performance name in the industry, the modern Hemi 5.7 had some big shoes to fill!
Perhaps overshadowed by the bowtie boys, the modern Hemi suffers only from a PR problem, as they offer every bit as much performance as their GM counterparts. Like the LS, both the 5.7L and 6.1L were blessed with impressive heads. The head flow allows the Hemi 5.7 to respond very well to even mild cam upgrades. Think of the modern Hemi as a motor equipped with race heads and a stock camshaft. Owners of small block (and some big block) Dodge motors would love the flow numbers offered by even stock Hemi heads, let alone ported versions (see the flow numbers in "Inside the G3 Cylinder Head," Oct. '12).
The boost came from HP Performance in Roswell, New Mexico, in the form of a single turbo kit. The kit was designed to bolt directly to the factory SRT8 exhaust manifolds and provide 7 psi of boost to the stock motor. The boost on this application was limited by the stock internal components of the motor and not the potential of the kit itself. As we will see in the second test, the kit offered exceptional performance on a dedicated application.
Impressed as we were with the result of adding boost to the stock motor, we decided to take things to the next level and really push the parts. To do this, we first needed a dedicated test motor, something that would withstand the rigors of elevated boost and power levels. Knowing that Hemi 5.7 truck motors are now becoming more common in wrecking yards, and that they make for impressive swap candidates in early Mopars, we decided to head off in that direction with our boost builder. After securing a Hemi 5.7 core motor, we tore it down and shipped it off to L&R Automotive for machining and prep for the Scat stroker kit. Though available and less expensive than the more desirable 6.1L, the displacement of the 5.7L was limited by the smaller bore size (3.917 versus 4.055). To increase the displacement, we increased the bore slightly (from 3.917 to 3.937) and installed a 3.795-inch Scat stroker crank (up from 3.58). The combination netted us a 6.1L-matching 370 cubic inches from our 5.7L junkyard turbo.
The forged steel Scat crank and 6.125-inch, 4340 rods were combined with a set of 0.020-over Probe Pistons. The pistons featured a 10cc dome to put the static compression ratio just under 10.0:1-a good compromise that would allow plenty of power in both normally aspirated and turbocharged trim. The assembled short-block was topped off with a set of ported 5.7L heads from Total Engine Airflow (TEA). Shipping our heads to TEA resulted in an increase in airflow from near 260 cfm to 315 cfm-more than sufficient to support our intended power levels. The stock valves were retained, but the heads were further upgraded with a set of 26918 valve springs and matching retainers from Comp Cams. The heads were secured using ARP head studs and Fel Pro MLS head gaskets. We selected a cam that promised to work well both in normally aspirated and turbocharged trim. The custom Comp hydraulic roller offered 0.589 lift (both intake and exhaust), a 239/247-degree duration split and a 114-degree LSA. The cam on our junkyard turbo was installed with the factory MDS lifters (though non-MDS lifters would be a better choice due to reduced weight).
In addition to the custom cam, Comp Cams also supplied a double roller timing chain assemb
Working with the new oil pump was a Milodon pan, pick up and windage tray designed specifi
The additional cubes and cam required additional airflow. The stock 5.7L Hemi heads were s
Once back from Total Engine Airflow, the heads were installed onto the awaiting Scat short
The stock 5.7L injectors were not going to get the job done on our turbo Hemi, so we stepp
The 5.7L Hemi was originally equipped with an electronic drive-by-wire throttle body. For