 Note the dramatic size and...  Note the dramatic size and obvious flow advantage over the stock Y-pipe and cats shown earlier. We reinstalled all four 02 sensors into the SLP headers and Y-pipe. A trade-off of losing some ground clearance (1-2 inches) was worth the significant gain of 22 rwhp. So far, we have yet to bottom out with the headers. |  As Ken finishes tightening...  As Ken finishes tightening the nuts and bolts (provided with the connectors) to complete the installation, you can see the crossbracing and where the connectors bolt up to the framerails and transmission crossbrace. Made from tough 14-gauge steel, these powdercoated beauties provide a tighter and more solid-riding F-body. |  The 400HP Pac adds over 75...  The 400HP Pac adds over 75 hp to a bone-stock LS1. With the additional power, we didn't want to chance creases in the quarter-panels while strip-testing. We needed a stiff chassis for consistent strip-test results without any unibody flex. SLP's bolt-in subframe connectors tie the front and rear of the car together with additional crossbracing to minimize T-top and dash rattles. |
 Spark-plug access actually...  Spark-plug access actually improves after bolting on the SLP headers. Before installing the EGR and smog pluming, we tightened all the header bolts from the inner to the outers. We made five passes on the bolts until they were all torqued to 18 ft-lb. We will retorque the header bolts (cold motor) after the engine goes through a dozen or so hot and cold cycles. |  While the T/A was receiving...  While the T/A was receiving the headers and connectors, we decided to treat the 84,000-mile car to a gear-oil change to Red Line 75W90 All-Synthetic gear oil. It contains an additive for limited-slip differentials and is claimed to provide increased gear protection, reduce differential temperatures, and improve drivetrain efficiency. |  We knew the only way there...  We knew the only way there would be enough bite to test the 400HP Pac was to get a pair of sticky meats. The Nitto NT555R Extreme Drag Radials (we ordered stock size 245/50R16) provide outstanding traction and handling on both the strip and street. The Nitto's are manufactured with a deeper tread (than other drag radials) and a hybrid compound for a 15,000-mile rating of normal use. |
 Considering the bad air (82...  Considering the bad air (82 degrees, 60-percent humidity) but great hook (thanks to the Nittos and E-town's crew), we were happy to run 12s with SLP's 400HP Pac. It was a load of fun testing each Pac and feeling the difference each step of the way. |  375HP Pac Dyno Results The...  375HP Pac Dyno Results
The LS6 intake brought a peak 17 rwhp at 5,368 rpm. Before the LS6 intake, the 375HP Pac was worth 310 rwhp; after, it was 327 rwhp or 392 hp at the flywheel. It's no wonder that the LS6-intake swap is so popular. |  400HP Pac Dyno Results The...  400HP Pac Dyno Results
The 400HP Pac was worth 22 rwhp at 5,353 rpm (peak). From 5,500 to 5,700 rpm (not peak), SLP's headers proved to be worth roughly 30 rwhp. The LS6 manifold and SLP headers put out nearly 40 more rwhp, making those bolt-ons well worth the effort and expense. We tried the SLP DiabloSport power tuner (from the 375Pac) but didn't see a change in power above 3,500 rpms. (We did observe a couple horsepower below 3,500 rpm). |