2005 Pontiac GTO Trick Flow Speciaties Cylinder Head Swap - Headstrong Poncho

The last part of the engine upgrade was fuel delivery. Since the stock fuel pump in GTOs are proven up to 475 rwhp, we decided to leave ours alone. The injectors, however, tap out much sooner, so we swapped out the stock 33 lb/hr units for a set of 42 lb/hr units from Summit Racing. Like most aftermarket units, the Summit injectors are of the Rochester design with an EV1 connector. However, the factory LS2 injector harness uses an EV6 connector, which is the later, more compact style and cannot be plugged directly into the Summit Racing injectors. But not all was lost as we were able to source up a set of injector wiring adapters from Summit under PN TFS-89201, $7.50 each.

So with a stack of boxes jammed into our GTO's miniscale trunk, we headed over to our friends at TT Performance Parts in their new facility in Little Falls, New Jersey for the installation and required tune. Proprietor Matt Sorian and the lead experts on this project, shop manager Nick Stevko and technician Jake Soja, spent a full day swapping out our top half and making the dyno sing. Once installation was complete, we topped off all the fluids, let the car run for a while to check for leaks or any other issues, and then strapped the car onto the DynoJet chassis dyno.

Previously, our Head Poncho cranked out 350.1 rwhp and 336.7 foot-pounds and blitzed to a 12.28 at 110.8 mph with just bolt-ons including a full Stainless Works exhaust that was expertly installed by TTP's own Rob Flores. But this time around, we were eager to see how our new engine package would perform as we listened to it settle into a nice, choppy idle. With our engine up to operating temperature, Sorian dialed in a good baseline tune and put the car at full throttle and we watched the rollers spin as our LS2 screamed to redline. Anticipation was high but we were quickly let down as Sorian looked at the chart in disbelief and asked us to come over and take a look for ourselves. With our mouths open, we stared at the graph that showed no gain whatsoever. Shocked by what was before us, we looked at the screen one more time to see what was going on and noticed that our power was actually going down as our engine speeds increased and the tachometer was hovering around redline during acceleration.

We quickly realized that all our newfound power was simply slipping away and that the stock transmission was more than likely the culprit. After a quick cooldown, we pulled out the transmission's dipstick and quickly smelled burned fluid, indicating that the 4L65E was pretty much toast. It was a true shame that with only 20,000 miles on the clock, our factory-original slushbox was unable to handle our new setup. Saddened, but not deterred, Sorian tuned our car the best that he could and we headed back home, slowly but safely.

A couple of days later, we found a used transmission on the Internet. Because of deadlines, we thrashed all night to install it at our home office and the next day, headed out to our favorite proving grounds, Raceway Park in Old Bridge, New Jersey. If we weren't going to be able to get dyno numbers by our deadline, we were sure going to do our darn best to get good track numbers. So with the Nitto drag radials lowered to 17 psi, we headed over to the burnout box and gave our shoes a serious heat cycle. Staged and ready to go, we stalled the converter up to 1,500 and once the last yellow lit, stomped the gas pedal and let the converter flash to an indicated 4,000 rpm (which is about 400 rpm more than we used to see.) Our short times were still terrific, with a 1.65, and by half track, we already knew we were in for a new best. Sure enough, the Goat cranked off an 11.334 at 119.22 mph-and we were politely asked to leave the premises due to the lack of safety equipment. Driving home, we were astounded at the numbers as we picked up nearly a full second and nine miles per hour!

Few cars offer the perfect combination of power, ET, handling and comfort-even in modified form-as well as the GTO. As we've demonstrated with our Head Poncho, the right combination of parts and state of mind with any GTO will result in a true turn-key weapon that can annihilate any car next to you, even from a standstill. So wait no longer, go pick up one of these cars, build it the way you want it, and realize how the latest GTO redefines its own legend.

By rotating the camshaft prior...        read full caption By rotating the camshaft prior to removal, Nick lodges all the lifters upward into their nylon alignment sleeves within the block. This keeps the lifters away from the cam and held in place while it is removed. In order to pull the camshaft out, you'll need to remove the radiator and air conditioning system's condenser. With everything out of the way, we then lubed up the TFS cam with fresh oil and slid it right into its new home and buttoned up the front with little fanfare.	After carefully cleaning off...        read full caption After carefully cleaning off the deck surfaces, we blew out all the head bolt bores with compressed air. This removes any oil or coolant that can cause catastrophic failure when the head bolts are re-installed. If you don't do this step, you will crack, or even worse, break the block by the upper mains. Trust us-we've learned the hard way in the past so take the time to do this right.	With the new GM MLS (Multi-Layer...        read full caption With the new GM MLS (Multi-Layer Steel) gasket in place, we moved the header out of the way and carefully lowered our new TFS heads into place.
The ARP head bolts were then...        read full caption The ARP head bolts were then lathered with the supplied moly lube and the metric bolts were torqued down in three stages-first to 25 lb-ft, then to 50 lb-ft and finally, to 70 lb-ft. The smaller perimeter bolts got 22 lb-ft.	With the FAST LSX intake manifold...        read full caption With the FAST LSX intake manifold installed (a practically direct replacement), we then focused on getting the valvetrain handled. First, we cleaned and oiled the TFS pushrods and inserted them into the engine. Then, we put the Harland Sharp rocker arms in place. Because each rocker arm pair shares a shaft for alignment and stability, you must tighten it down carefully so that it goes down evenly. If you do not, you risk bending the shaft, which of course, is not a good thing as valvetrain damage may occur. Nick took his time here and had it all together just a short while later.	Anytime you perform any internal...        read full caption Anytime you perform any internal engine work, always put in fresh motor oil. Of course, spin on a new filter while you're at it.
With our GTO back on the dyno,...        read full caption With our GTO back on the dyno, we were eager to see what the result of our full day's work would be. After Jake Soja completed the run, we already could tell things weren't good as the transmission quickly gave up the ghost as it slipped under all the new power. Despite the bad news, Matt Sorian, master tuner and big cheese of TT Performance, gave us a solid tune anyway so that we wouldn't have to worry about it later. This would allow us to limp the car back home, swap in another transmission (a used one we found online) and bring it right to the dragstrip in time for our deadlines.	Back at Raceway Park in Old...        read full caption Back at Raceway Park in Old Bridge, New Jersey, we quickly aired down our Nitto Drag Radials and made a pass down the fabled 1320. As soon as the car lunged and took off, we already knew we were in for one heck of a ride. Without even so much as a cooldown, our first pass netted us a stout 11.33 at 119 mph. Unfortunately, we were asked to leave due to the lack of safety equipment, so we couldn't make any further attempts to better our times. But with nearly a full second of improvement and an equally impressive nine mph gain, we were looking at an estimated 100 horsepower more than before. Hooray for heads!