2005 Pontiac GTO LS2 - Spicing It Up

The power potential built into each and every late-model LS-powered Pontiac is widely known. With their exceptional cylinder-head flow, compact dimensions, great strength, and hunger for nitrous, the Gen-III and IVs have proven to be great foundations for street/strip combos.

In 2005, the 5.7-liter LS1 was replaced with the 6.0-liter LS2 in the GTO, giving it a 50 hp increase. The Goat flexed its muscles in a big way and lured Bill MacKenn into a Pontiac showroom in February 2006 for a little spice.

Knowing that the GTO wouldn't see production for 2007, he wanted his to be special. Pontiac releases a handful of new colors each year, which makes certain hues extremely rare. For the final production year, the new colors were Brazen Orange Metallic (66U) and Spice Red Metallic (71U). After seeing the 71U color sample, Bill checked it off along with a Tremec T56 manual and the optional 18-inch wheels.

Round 1
Engine modifications began by improving induction and exhaust flow with a K&N cold air intake and Dynotech 1.75-inch stainless headers and high-flow cats. Bill was looking for a unique sound and an exhaust his GTO could grow into, so he had Rainbow Muffler in Largo, Florida, make him an emissions-legal custom 3-inch system all the way back with 3-inch Flowmaster 40-series mufflers, and using the stock tips. The sound can only be described as "GTO" since it sounds like every Goat should.

Hunting for more power, Bill had Tiberio Performance of Tampa install a custom 224/228-degree duration, 0.595/0.595-inch lift, 112-degree LSA cam with Comp Cams 918 springs and hardened pushrods. He then went to Nitrous Dave's website to order one of his dry kits for an additional 125 horses. The system was installed with a window switch and bottle heater. To increase the fuel flow, an in-tank Walbro 255 lph pump, Siemens 60-lb/hr injectors, and Aeromotive fuel rails were added.

When strapped down to the dyno, the spicy GTO generated 516 hp and 512 lb-ft of torque at the wheels with nitrous.

To reliably put the power to the pavement, the transmission and 3.45-geared rearend were upgraded. Bill toasted a handful of clutches before finally settling on a Monster stage 4, which he feels holds the power and is very smooth to actuate. He didn't want to miss any gears so a GMM Ripshift shifter was installed, which dramatically reduced the knife-in-a-mayonnaise-jar feel of the factory piece.

Out back, the notoriously weak factory differential was strengthened with a Harrop cover and BMR axles and stubs. Bill briefly used a stronger driveshaft but has gone back to the factory setup. To date, he hasn't had any issues beyond a few failed clutches. A pair of BMR drag bags, filled to 14 psi, inside the rear springs reduce wheel hop. They help to preserve the drivetrain and a BMR driveshaft safety loop is there, just in case.

Round 2
After finding great success with his old setup, Bill was enticed to push the combo to the next level. A Futral Motorsports F-14 camshaft with 232/234-degrees duration and 0.598/0.598-inch lift on a 112 LSA was installed by Tiberio Performance. When Comp Cams' 918 springs initially had a problem in this combo, Comp stood behind its product and sent Bill a set of 921 springs at no charge. These new springs are rated for 0.650-inch lift.

The Goat was taken over to Precision Motorsports of Florida in Odessa, where Bob Morreale ported a new FAST intake manifold and mated it with a Fasterproms-ported factory throttle body. This was installed along with a pair of Dart LS1 PRO1 cylinder heads that he hand-ported. They now flow 315cfm intake and 245cfm exhaust at 0.600-inch lift and use 2.08/1.60 stainless valves. The compression ratio is 10.9:1 with the new heads.

The nitrous was also bumped to 175 horse-power before the Goat took to the rollers again. According to Bill, it generated an outstanding 657 hp and 732 lb-ft of torque on nitrous and 457 hp/443 lb-ft naturally aspirated.

Both Bill and Bob felt the nitrous numbers were a little risky on the stock bottom end. They made adjustments to the nitrous to bring the torque below 600. The final result was 596 hp and 592 lb-ft of torque, just where Bill wanted to be. "I think the car has more than enough power to bring me into the 10s now," he quips.

Bill's tuning was previously done by Jeremy Formato at Fasterproms in Tampa, but he got tired of having to make alterations to his tuning because of his nitrous setup. "I was very happy with the tune on the street but I had to have it retuned if I wanted to spray the nitrous," he adds. "So I wanted to learn how to tune the car myself." He enlisted in The Tuning School's Tampa seminar to learn everything he needed to know about how to use engine-tuning software like HP Tuners. The class actually used Bill's GTO as a testbed for a true hands-on experience. He now has the luxury of tweaking his control modules as he sees fit and no longer has to worry about making a sacrifice for a street or a track tune.

Since the power numbers had swelled, further attention was placed on the chassis. The drag bags were a big help, but there was still more to be done. Up front, Precision Motorsports installed a BMR strut-tower brace, Pedders HD strut mounts, strut bearings, and radius rod caster bushings. A pair of 5/16-inch raised rear coil springs, GSR shocks, and X-member bushings complete the rearend setup, while new sway bar bushings all around improve cornering. When all the work was done, the rear cradle was aligned and Bill was on his way.

On the street, the GTO wears a set of factory 18-inch wheels that were chromed by Courtesy Pontiac in Tampa. They're shod in 235/40-18 BFG G-Force Sport tires up front and 275/40-18 Falken FK-452 in the rear.

What's In Store?
Now that the GTO is dialed in, the 52-year-old Pasco County Deputy Sherriff is gunning for a 10-second timeslip. His previous best came at the 2008 All GTO Track Day with his old camshaft, LS2 intake, and BMR Drag Bags. On 275/40-17 Mickey Thompson Drag Radials and shifting at 6,300 rpm, he went 11.2 on a low 1.60 60-foot, spraying out of the hole and at a race weight of 4,100 pounds. Later in the day, during eliminations, he launched the IRS-equipped GTO perfectly and was rewarded with a 1.59 60-foot. This ended up being the best 60-foot by any manual transmission Goat at the event and he was given a trophy to commemorate his achievement. "I just bring the rpm up to 3,500 or so and then bring the clutch pedal out just prior to engagement. When the tree drops I give it a quick release and off I go," he comments on his launch technique.

Bill is confident that his power level and driving experience will pay off with a membership to the 10-second club in the near future, which will certainly confirm that plenty of spice has been added to his GTO.