 Here's where we connected...  Here's where we connected the fan-switch wire into the wiring harness on top of the right-front fenderwell. The gray wire in the top-right of the picture is for the three-way fan switch. |
 We poked the gray wire through...  We poked the gray wire through a pre-existing grommet in the passenger-side firewall and fed the wire towards the steering column where we would install the fan-control switch and the ground was connected. These are the basics, the instructions will fill in the rest. |
 Mounted below the instrumentation...  Mounted below the instrumentation and above the OBD-II port is SLP's fan-control switch, which has three positions; stock (thermostatic), low-speed, and high-speed. The fan switch helped lower the coolant temp a consistent 160-170 degrees between runs on our tractionless track-day test. |
 The 350HP Pac produced 289...  The 350HP Pac produced 289 peak horsepower at 5,113 and 305 lb-ft of peak torque at 4,102 rpm; average horsepower was 253 and torque was 298 lb-ft. SLP's 375HP Pac produced 310 peak horsepower at 5,217 and 318 lb-ft of peak torque at 4,200 rpm; average horsepower was 270 and torque was 312 lb-ft. Air inlet temp at the induction scoop was 94.5 degrees for the 350HP Pac; for the 375HP test, it was 98.7 degrees. Coolant temp was 170-179 degrees for best rwhp while testing both Pacs. |
 The crusty sight of the stock...  The crusty sight of the stock thermostat housing on this daily-driven LS1 caused us to change it as well as the thermostat. We cleaned the surface area (water pump housing) and didn't forget to use the supplied O-ring before bolting it back together. It can take some time to completely refill the motor with coolant by letting it run and purging the air-steam pockets. We kept a close eye on the temp gauge after each of the first few drives, and we rechecked the coolant level after it cooled. |
On the ride home, the trans shifted like we just changed the valve body (much quicker and firmer), and the temp gauge never went over 180 degrees, unlike before when it would hang near 210 degrees.
We drove the T/A 90 minutes to meet our co-workers from GM High-Tech, Super Chevy, and Muscle Mustangs & Fast Fords magazines. They arranged for a test day at our favorite track, Raceway Park in Englishtown, New Jersey. Our test day was in typical hot August weather, so we popped the hood and flipped the fan switch to let the Bird cool down for an hour.
Before we began testing, the temperature was a warm 86 degrees. Our front tires were inflated to 40 psi, and the rear were deflated to 28 psi. When we factored the 350HP Pac's 13.10 baseline from that 65-degree test day, our new baseline was 13.22 for this 87-degree day.
We pulled up to the line and slowly stepped into it coming out of the hole, but now the tires were spinning too easily from the newly added power. I looked up and noticed a lousy 2.20 60-foot time but continued down track to a disappointing 13.30 at 106.07. I came back for a hotlap and stepped into it even more slowly, and the tires still spun worse to a 2.23 60-foot with a 13.37 at 105.91. For the rest of the day, no matter how gently we tried to come out of the hole, we were 0.3 off our 60-foot times from when we tested the 350HP Pac.
Besides the added power causing traction woes, the owner replaced one of the rear tires (four years ago; stock size 245/50R-16) with a different brand (and therefore, a different tread and compound), so the tires weren't working together. The fronts were also worn too unevenly to rotate, and nobody had a pair of sticky tires to lend us. This was a real-world occurrence that even happens to us magazine guys.
Conclusion
Once again, we were impressed with SLP's PerformancePac. This time, the Stage 2 package was "put to the test" and delivered the goods on the dyno. The added power to the pedal with the old hard-compound radials made our strip test impossible but was much more fun on the street. With slicks or drag radials, we're sure 12s would have been possible. Tune in next time for the 400HP Pac installment and test-with good tires.