2005 Pontiac GTO Bolt-On Upgrades - A Sixer For The Road

The 1.75-inch primaries feature smooth mandrel bends with a 3/8-inch laser cut flange attaching them at one end. At the other, the four-into-one style collector measures 3 inches in diameter...

...The Stainless Works headers also boast some very impressive welding to complement the solid stainless steel construction.

With a little finesse, Junior manages to get both sides in. On the driver side, the steering shaft needs to be tucked out of the way while slipping the header into the engine bay from underneath...

...Then once in place, the reused stock manifold gaskets are slipped in between the headers and the six 13mm bolts are treated to some blue Loctite and torqued to 18 lb-ft. The steering shaft has to be threaded through the primaries in order to be reconnected to the steering rack.

For some reason the intermediate pipes, which connect the cats to the crossover, did not line up with the flange. The design of these headers and pipes has them hugging the floorpan nicely for increased ground clearance, but unfortunately it was causing a fitment issue with the rest of the exhaust and our driveshaft loop. Stainless Works sent us a fresh set of pipes that had been test fit on one of its test cars, however, ours was a no-go. Perhaps it was the Sport Exhaust or maybe our catback was more mangled and twisted from the factory (to clear the IRS). Lucky for us, with a set of off-road pipes there was enough play in the piping to connect the headers to the crossover with the provided clamps securing the two pipes to each other. As expected, this caused the "check engine" light to come on and also a "check oil" light, which may or may not be related. Ed Wright from Fastchip has informed us that at least the "check engine" light is fixable through programming, so we may have to send the PCM back at some point. We plan to resolve these issues as soon as possible, but so far we have not experienced any adverse effects from these problems.

In between removing the OEM manifolds and installing the headers, Junior removed the spark plugs since we had planned to change them anyway...

...This also gave a little extra wiggle room when installing the headers. The stock plugs looked good, but we didn't want to put anything to chance with nitrous.

Once the NGK TR6s were gapped to .040 and installed, on went the new MSD 8.5mm plug wires with a generous helping of dielectric grease. The new wires use factory style plug boots, so they were a perfect fit. The design of the Super Conductor wires allows for low resistance to maximize spark energy without generating EMI noise that could potentially interfere with other electronic devices on the vehicle.

On to the intake, the clamps can be loosened, the airbox unscrewed and removed. The crankcase vent hose must be disconnected along with the coolant fill lines, but first, the plastic radiator cover must be removed via its five clips before the bottom portion of the airbox may also be removed along with the Torx T27 mounting screws.

The intake elbow pulls right off once the clamps are loosened.

The nitrous and fuel lines need to be disconnected along with the wiring harness for the nitrous system to maneuver the MAF as needed. A gasket (provided in K&N's kit) goes in between the MAF and the heat shield before screws thread through all three and into the adapter, which the filter mounts to. Since this kit is obviously designed to fit a stock MAF, the screws are not long enough to thread through the billet nitrous plate/MAF that we had installed...

...And since the billet plate has threaded holes, it makes it impossible to fully tighten. Junior solved the problem, though, by drilling out the holes and finding some longer screws.

The heat shield/MAF assembly is then put into place along with the filter, and the clamp is tightened. A 10mm socket is sufficient for securing the heat shield to the chassis via the bracket, however it is best to leave a little loose for now.

Once the intake elbow is wiggled into place and the clamps are tightened, then the 10mm nut can be tightened on the bracket and the rest of the connections can be reestablished such as the MAF and nitrous system--and the job is done.

While removing the screws from the airbox, Junior found it easier to remove the PCM via its 13mm nut and plastic clips. The Fastchip-tuned unit was put in the stocker's place, and voila! Instant tune up.

Since the cramped wheelwells of the GTO would not allow for any tire larger than stock, we had no choice but to stick with 245/45R17 Nitto 555R drag radials. The Nittos are designed with a soft compound for maximum traction yet still provide 15,000 miles worth of tread life, so you can still drive them on the street. For the weak rear-ended GTO, this is the safest bet in terms of racing, yet you can still appreciate its practicality. A day or so later, we headed down to Englishtown and confirmed the softer compound's advantages over the stock all weather tires with a 1.97 short time--the best to date by a full tenth.

After posting a new best ET of 12.85 at 110 mph (previously 13.20 at 106 on motor), we headed down to SLP Performance in Toms River to compare the updated Goat with its stock numbers on SLP's SuperFlow dyno. Since SLP is equipped with all of the latest software, we could even take a peek at the ignition timing and air/fuel ratio.

According to SLP's instrumentation, about 28 degrees of timing was being run into the LS2, however, between 3 degrees and 4 degrees of retard was being detected as the air/fuel ratio leaned out to just under 13.4:1 between 3,000 rpm and 5,000 rpm. This tune would have been perfect for a car with cats, as we had told Ed Wright at Fastchip that cats would be used. However, since we had to use off-road pipes it threw off the tune a bit. Nonetheless, 375.9 hp at 5,704 rpm and 372.7 lb-ft of torque at 4,775 rpm was seen at the wheels. That is a gain of 34.8 hp and 38.8 ft-lb with more power left on the table. We expect to see an increase in power with a fresh tune designed for the offroad pipes. But for now, we will have to be happy with our 440 flywheel horsepower and call it a day.