In terms of the oiling system, we installed a new stock oil pump, but augmented the system with a Milodon oil pan, pickup, and windage tray. In preparation for Part 3 of this adventure, we welded a drain tube in the Milodon pan for our future turbo motor. We also replaced the factory injectors with a set of 75 pounders using the stock fuel rail. It was necessary to install spacers under the rail to make room for the taller injectors. As with the 5.7L cam test, we utilized a set of SRT8 exhaust manifolds feeding short extensions. Long-tube headers would help this combination substantially, but it was interesting to see the power produced with the stock manifolds. Another carryover from our original 5.7L cam test was the manual throttle body (converted from drive-by-wire). The motor was run with both the stock plastic truck and STR8 aluminum intake manifolds, and both managed to produce the same peak power (with both cams). This came somewhat as a surprise, as we expected the truck intake to offer more low-speed power but lose out on top compared to the SRT8. Run with the 260H-13 cam, the 370-inch stroker 5.7L Hemi pumped out 454 hp and 453 lb-ft of torque. True to form, torque production from the stroker exceeded 425 lb-ft from 3,900 rpm to 5,600 rpm. Best of all, the stroker improved the power output (over the 5.7L) throughout the rev range, offered improved idle quality (with the same cam), and looked just like the stock motor. The additional displacement increased the power output by 53 hp and 26 lb-ft over the 5.7L equipped with the same cam (the 5.7L produced 401 hp and 427 lb-ft in Part 1).
Despite our success with the stroker combination, we couldn’t help but wonder if the extra cubes might respond to wilder cam timing. Additionally, would the expected improvements in peak power come with a penalty down low? To find out, we installed a much more aggressive cam profile. The custom hydraulic roller cam from Comp Cams featured .589 lift (both intake and exhaust) and dual-pattern duration specs of 239/247 degrees at .050. The LSA checked in at an idle-friendly 114 degrees. As we experienced in Part 1, cam swaps on the Hemi were a breeze on the engine dyno. After the swap, the new cam offered some serious power gains, increasing the peak numbers from 454 hp and 453 lb-ft to 526 hp and 451 lb-ft. Impressive as the numbers sounded (and they were), they did come with a cost. The trade off for all that top-end power was a loss in torque below 5,100 rpm; as much as 38 lb-ft. Which cam offers more appeal depends a lot on the intended use. If you are looking for maximum acceleration, then the big cam is the way to go, but most street drivers might be better served by the smaller cam. Of course, you can always venture somewhere in between. Check back with us next month, when we take our boost-ready stroker and pump up the volume with a single turbo kit.