The first order of business...
The first order of business was to strap the '05 GTO onto our Dynojet 224xLC and see what it registered. Running the LS2 to 6,500 rpm, the best of our four pulls generated 367 rwhp and 361 lb/ft of torque, providing us with a baseline.
Our LS2-powered GTO has always been a strong runner with 400 hp on tap, and represents one of the shining moments of GM build quality and performance, so it may come as a surprise that anyone would want to tear it apart in an effort to make it even quicker. Regardless, it's all we could think about for months after participating in a Performance Driving Event at Sebring.
Since this Goat was built mainly for taking corners, Jonathan Blevins, our instructor from Track Guys, told us to seek a realistic power level. He warned that increasing the power would have repercussions on the road course. It demands better cooling, more durable driveline parts, and even larger brakes. In a nutshell, the more power you make, the closer you have to look at everything down the line to make sure it can be utilized effectively.
The advice to make only moderate upgrades follows the theme of the GTO, as we haven't wanted to cut into it or do anything too radical to achieve our goals. Therefore factory-sized 245/40R18 Nitto NT01s sit on all four corners, which limits the overall power that can be effectively held on the track and the cornering speed. This is all fine and dandy because the GTO is driven every day and sees a lot of street duty to and from the office and around town.
Since the LS2 uses a 4.00-inch...
Since the LS2 uses a 4.00-inch bore, we could have used the budget L92/LS3 head that offers very good bang for the buck. After talking with Trick Flow, however, we were convinced that the traditional cathedral-port style of the stock heads and the Trick Flow GenX 225 was the way to go, especially since we wouldn't need to find a new intake manifold. The cathedral port is said to deliver better low-end power yet doesn't get choked-up on the top-end. Rectangle ports are said to make more power up top and slightly less torque.
Looking for a moderate power boost, we contacted Trick Flow Specialties to discuss our goals for the GTO. David Canfield, Trick Flow's marketing coordinator, met with his staff and suggested the Trick Flow GenX Top-End Engine Kit for the LS2.
The company has paired its GenX 225 cylinder heads with its own custom-grind camshaft, 7.500-inch hardened pushrods, and Harland Sharp 1.7:1 roller rockers. Air is ingested through the enlarged 225cc cathedral ports. The heads feature refined, fully CNC-machined 65cc combustion chambers, which retain the factory 11.0:1 compression ratio and evacuate the exhaust gases through the enlarged 80cc exhaust ports. Two of the keys to Trick Flow's head design is its 13.5-degree valve angle and three-angle valve job-in layman's terms, just a lot of good stuff inspired from heavy race technology.
The heads come assembled and ready to install with lightweight stainless steel valves, 1.300-inch-diameter high-lift dual valvesprings (rated conservatively for 0.600-inch lift), titanium retainers, 7-degree locks, Viton valve seals, and ductile-iron valve seats. These heads also retain full functionality of all stock sensors and fittings and can accommodate aftermarket roller rocker arms without the need for valvecover spacers. Trick Flow always suggests using full roller rockers when a cam with larger than stock lift is installed to minimize valve deflection.
These heads are marked with...
These heads are marked with 225 CNC to identify the intake runner volume. They're also available with more affordable Fast as Cast runners, which feature all the same goodies as the CNC heads, but at a more affordable price point and flow nearly as much."
These heads move a lot of air-considerably more than the stock LS6 heads. Because of this, we are able to run a camshaft that's slightly milder than what is usually included in the kit, and still make terrific power while retaining driveability. This kit usually comes with its Track Max TFS-30602004 cam (aka #4). It's rated at 238/242-degrees duration with 0.595/0.595 lift and an LSA of 112 degrees, and was determined to be a little more than we needed to reach our goals of mid 400rwhp. Trick Flow, by request, can substitute any of its Track Max LSX camshafts, and substituted the #4 cam with its TFS-30602003 cam, (aka #3). The specs on the #3 are still very impressive, but slightly tamed with a 228/230 duration at 0.050 and 0.585/0.585 lift on a 112-degree lobe separation. Its powerband is rated for 2,500-6,500 rpm, which is pretty much everything we're going to see at the road course or dragstrip.
Trick Flow includes most of the major components required to successfully swap our cylinder heads and camshaft. In addition, we purchased two water-pump gaskets and a front timing cover gasket for a total of about $40. Also, because of our mileage and driving habits, David sent over one of Trick Flow's Adjustable Double Roller timing sets.
Once the parts were delivered, D Revolution Motorsports in Davie, Florida, offered to perform the swaps in our recently retooled and renovated High Performance Pontiac Tech Center located in Tampa.
In this installment, we're discussing the attributes of the new parts, why we chose them, and we begin the teardown. For the next issue, we will cover the remainder of the teardown and then the assembly with the new components. Finally, we'll move on to tuning and dyno testing.