Few cars in modern automotive history are as much of a total package as the modern GTO. With an incredibly stiff chassis, great handling characteristics, and seamless LS power, it is a true match made in GM heaven. Getting behind the wheel only proves this point further, as the GTO is always in full control, no matter how hard that go-pedal is stomped. The GTO can easily handle 500- or even 600-horsepower or more and still be as controlled and easy to drive as it was when it was bone stock.
So, wanting to test the limits for ourselves, we set out on a horsepower pursuit to eternal dragstrip happiness by adding more power to Head Poncho, our resident 2005 GTO. While there were many ways to go about it, we decided to keep things simple-almost scientifically simple-so we left the car naturally aspirated to avoid any more weight gain to our already heavyweight hitter. Going the all-motor route would also reduce the amount of down time required as we wouldn't have to spend days tuning it if it had a forced-induction setup. So, the hunt was on for a free-breathing top half to complement our 6-liter pony eater.
With our goals laid out, we looked for a top half that would offer the perfect balance between power, reliability, torque and oh yea, power. (You can see our priorities, can't you?) To get these results, the centerpiece to our horsepower recipe was going to rely heavily on our cylinder head choice so we didn't bother playing any games and went straight to the awesome TFS GenX pieces. These heads have 13.5-degree valve angles and come fully assembled with 7-degree titanium retainers for immediate installation and no hassles (however, they are also available bare should you want to use your own valvetrain.)
Currently, TFS offers three versions of its fully assembled, CNC-ported GenX aluminum cylinder head, with each easily identified by their intake runner volume. The 215cc, 225cc, and 235cc versions denote their ideal applications as each one of these has a correlating valve size to match a particular engine's breathing needs. For instance, its 215cc units are ideal for the 5.7-liter LS1 as the 2.040/1.575 valves clear the smaller bores perfectly. With our LS2's larger 4.0-inch bore we were able to take advantage of TFS' larger 225cc castings with their upsized 2.055/1.575 valves. The even-larger 235cc versions are best suited for stroked or force-fed applications, which we rightfully admitted to ourselves as being a bit more than we really needed. So, with the 225cc units added to our shopping cart (PN TFS-3060T001-C02, $2,395) we then grabbed a pair of new GM head gaskets and ARP head bolts (PN 134-3610, $113). With our head selection finished, it was time to move ahead with our camshaft choice.
For our moderately aggressive 225cc heads, we went with TFS' Track Max camshaft (PN 306-02003, $339). It checks in at a healthy 228 degrees of duration at .050 lift on the intake and 230 degrees on the exhaust. Lift is pretty stout at .585 on both sides and keeps the valvesprings happy by staying below their .600-lift limit. In addition, the cam is designed to provide maximum power and torque without any valve-to-piston interference, especially at the upper reaches of the tachometer. With our head and cam package selected, it was time to move ahead to the supporting valvetrain components and an intake manifold upgrade.