One of the primary modifications made to increase power output is a custom C4orce camshaft ground by Comp Cams. We were more interested in mid-range than top-end power, so we kept duration rather conservative. Rated at 0.050-inch valve lift, this cam has 220 degrees of intake and 224 degrees of exhaust duration. While those specifications might seem extremely mild, the engine's response proved that they're nearly ideal. Low-speed and mid-range driveability are excellent, and there's just enough lope at idle to draw admiring glances from anyone who hears the exhaust.
Additional breathing enhancements are derived from the original 5.3-liter cylinder heads, which were pocket ported by Pete Incaudo of VMax Motorsports. Owing to the budget constraints of the project, Incaudo elected to do a mild port clean-up and precision valve job rather than a full CNC port modification. After installing the modified heads, we added an LS6 intake manifold, which we fortunately had left over from another project. The final piece to our intake system puzzle is a CNC-modified throttle body from VMax.
While an LS6 intake manifold is preferable for any performance-oriented engine, it's certainly not essential. The LS1 manifolds found on '97-'00 model-year engines are perfectly acceptable. While they might not provide the LS6's ultimate power potential, their cost makes them extremely attractive. Used manifolds in excellent condition are available for $30 or less.
The final piece in the puzzle of bringing a transplanted LS-style engine to life is the electronic engine controller, which must be reprogrammed to function in an environment that's dramatically different from the one in which it formerly operated. The required changes are readily made with FlashScan software from EFILive. We opted to eliminate the mass-airflow sensor from the Project C4orce engine installation, so the first order of the day was to convert the PCM to operate in speed/density mode. We also had to turn off some of the diagnostic tests (because they were no longer applicable) and reconfigure the tables that control fuel delivery and ignition settings.
Idle and part-throttle operation are typically the most time-consuming aspects of reprogramming an ECM or PCM for a modified engine. Fortunately, the testing required to optimize these settings doesn't require a chassis dyno. (In fact, it can't be done on a chassis dyno, unless the unit in question has the capability of operating in steady-state mode.) Wide-open-throttle operation is a different matter entirely, so after finalizing the idle and part-throttle settings, we headed to Atlanta Chassis Dyno for a maximum-power test session.
Considering the engine's displacement, camshaft, and cylinder heads, we were expecting maximum hp to fall in the 300-325 range. To our surprise, the engine cranked out 349.75 horses at 5,800 rpm and peak torque of 336.17 lb-ft at 4,800 rpm. The peak-torque figure was in the middle of a broad, flat curve that exceeded 310 lb-ft from 3,500 to 5,800 rpm. (These figures incorporate the SAE [net] correction factor.)
If you're used to looking at the torque curves of tuned port engines, you'll notice that the 5.3's torque peak is achieved at relatively high rpm. That's a characteristic of LS-series engines. A completely stock 5.3-liter engine, with an absurdly mild camshaft (190 degrees of duration measured at 0.050-inch lift) produces peak torque at 4,000 rpm. It's also worth noting that a stock LS1 only produces about 300 hp at the wheels, while an ('02-'04) LS6 cranks out around 355.
In spite of the exceedingly long time it took to complete Project C4orce, the results are gratifying. They also provide a blueprint for anyone wishing to undertake a similar project. Whether the engine of choice is a 5.3-, 5.7-, 6.0-, 6.2-, or 7.0-liter model, the basic mechanical steps are the same. And the end result will be a truly unique Corvette.