The Manley-crafted connecting...
The Manley-crafted connecting rods were also beautiful and lightweight. These are their "Tour Lite" I-beam rods in a 6.125-inch length. They ship with ARP 2000 bolts and are bushed for use with a full-floating piston. These rods carry PN 15345C-8 and are a great choice for serious LS powerplants. The average big end weight on these rods is 368g; the pin end average is 175g.
Once we'd received four camshafts to test (with minor deviations in lobe centerline, duration, and overlap) we found the best numbers using a Cam Motion grind with 255/262 degrees of duration at .050-inch lift, and .707 and .680 inches of valve lift on the intake and exhaust sides, respectively.
Our reciprocating assembly choices were twofold. We ordered up a flyweight (40.3-pound) custom crank from Callies to minimize reciprocating mass, and hoped that this crank (teamed with lightweight Manley forged rods and custom-crafted 459g CP pistons incorporating ultrathin .032-inch-thick Total Seal top and second rings) would deliver more power than heavier, more readily available parts. It's certainly proven to make a difference in the acceleration rates of competition cars that have powerplants so equipped. But these parts would require waiting while they were being crafted, so we went with more pedestrian parts to complete the testing. We'd go through the rebuild once again just before the Challenge competition, and drop our flyweight "jewelry" into the crankcase at that time. Since the basic dimensions (crankshaft stroke, connecting rod length, piston pin height) would remain identical, this was a solid plan and we'd be able to see the benefit of the lighter parts in back-to-back testing.
After testing several different...
After testing several different headers, TPIS found the best average power and torque with these pipes from American Racing Headers (ARH). They're a step design, going from 1.750 to 1.875 inches before tapering down to a 2.5-inch collector choke.
Unfortunately, we didn't see the substantial power gains we'd hoped for post-rebuild. We did see 5-plus horsepower across the board, but considering the substantial investment these lightweight parts command, the power benefit hardly seemed worthwhile. We reasoned that the true benefit of such parts (faster rate of acceleration) was snuffed by the computer-controlled acceleration rate on the dyno.
Additionally, this final pre-Challenge rebuild would give us the benefit of inspecting all of the engine's internals to ensure all was up to snuff right before the competition. Once accomplished, everything was found to be just fine. The only work done (besides the previously mentioned reciprocating assembly swap) was a tiny touch on the valve seats. They didn't really need it, but as Myron says, "After 600 dyno pulls, I had to touch the valve seats. It was just for insurance, so I could sleep knowing they were as good as they could be." No other changes were made to the heads.
The headers also boast an...
The headers also boast an intricately formed goilet where the four primary pipes join as they enter the collector before feeding into MagnaFlow mufflers. The quality of these headers is first-rate, from the pristine clean welds, to the thick flange mount where they bolt up to the heads.
One area we admittedly should have invested more attention in was the oil pan. We used a factory "truck" oil pan, and after speaking with other LS-based competitors at the Challenge, this may have cost us some power.
"We should have just made an oil pan," Cottrell says. "The truck pan we used has a deep sump, but the front of the pan is quite close to the crankshaft. I think that might have been an issue, and some clearance there may have helped a little." As it was, using the stock pan and stock pickup with oil pressure limited to 45 psi, there were no lubrication issues after hundreds of 7,000-rpm pulls. The setup works reliably, but there may be more power on the table here. The engine was broken-in using Gibbs Break-in Oil, which proved to work extremely well compared to typical parts store oil typically employed for this purpose.