Upon release of the 2004 GTO many aftermarket companies were scrambling to figure out how to make a 3,800-pound car with IRS satisfy the demands of the General's army of drag racers. BMR Fabrication was by far quickest out of the hole, placing its order for the Australian built Poncho over a year in advance, and in January 2004 they were among the first in the state of Florida to receive one. BMR's intentions were simple: to make quick discovery of any potential weak links in the driveline and suspension, and in the process become the first 9-second GTO.
After taking delivery of the A4 Impulse Blue GTO, it was put up on the lift for inspection of the stock drivetrain and suspension. Since GM was very tight-lipped prior to its release, BMR didn't have any idea what to expect from the Holden-based coupe. "Immediately apparent was the weak driveshaft, which utilized flimsy rubber bushings in lieu of U joints," said BMR owner Brett Rockey. BMR's solution was a three-inch steel driveshaft with a Mark Williams billet front yoke and a Spicer 1350 U-joint flange. An adapter was required to convert the domestic U-joint to the Aussie splines. In addition to eliminating the flimsy U-joints the diameter of the driveshaft was increased by a full inch, BMR also now offers this unit in aluminum and carbon fiber to handle increased power and rpm.
Independent rear suspension would be another hurdle for BMR; while great on the road coarse it is prone to axle-breaking wheelhop on the dragstrip. BMR was proactive with 300M billet stub axles and CV shafts before turning the OEM units to confetti, which Brett said usually happens when sixty-foot times get around 1.6 seconds. A set of subframe connectors was also fabricated as preventative maintenance, Brett says this is usually the first thing he does on any unibody.
"It allows the suspension to do its job more efficiently and eliminates creaks, rattles and misalignments further down the road." The GTO's unique rear suspension utilizes a cradle, which is sort of a rear K-member, to connect the rear suspension and differential to the body. This made connecting the front and rear subframes difficult because welding the connectors in place would prevent the removal of the differential. However, BMR found that creating new cradle mounts resolved this issue and, along with spacers for the body to subframe mounts, helped eliminate wheelhop. When combined with a Harrop differential cover to provide added fluid capacity and a more stable mount for the rear cradle, it seemed the rear end was near bulletproof. As they say, though, there is only one way to find out.
To truly test the driveline and suspension components the Goat would have to be running well under 1.7-second short times. To this end a Precision Industries Vigilante torque converter, TransGo shift kit, drag radials and a few bolt-ons were added but this only got them to 1.77 on the way to 13.19 in the quarter. It was time to get serious and since the '04 GTO had only been on the street for a month, this left little choice but to go with nitrous, which as Brett pointed out is "extremely versatile." The LS6 manifold was then shipped over to Applied Nitrous Technology for a custom direct port kit capable of over 300 horsepower. The system utilized Nitrous Express solenoids and nozzles along with a supplemental fuel system. A stand alone fuel cell took the place of the battery, which had to be relocated to the trunk, and was fitted with an Aeromotive low pressure fuel pump to supply the wet nitrous jets with 103-octane race gas. This was decided to be a good time to also add an MTI 75mm billet throttle body and a Meziere electric water pump.
The new combination required some tuning, so the Goat was brought over to Jeremy Formato at Rev Extreme. Unfortunately the early production PCM proved quite troublesome, but finally came alive when Jeremy switched to a speed density system using HPTuner. Naturally aspirated numbers climbed by 20 horsepower, Brett said, and after increasing the jetting several times BMR's GTO made 536 rwhp and 497 lb-ft of torque. To resist detonation with the juice BMR went two steps colder with a set of NGK spark plugs and installed a Ramchargers Timing Tuner to retard timing. An MSD RPM Window Activation Switch was also used to enable trackside adjustments to the rpm triggered activation of the nitrous. At an MSD True Street event the Goat broke the 11.50 mark and cut a 1.59 sixty-foot. They had tried lowering the activation rpm and even using Mickey Thompson ET Streets, but neither proved to be effective. BMR knew they weren't going to get much further on the stock motor, so plans were made for a stroker with a bulletproof bottom end.
In the mean time, BMR would push the stock motor as far as they could by installing a brand spanking new FAST LSX intake manifold with Applied Nitrous Technology plumbing. A set of LS1Speed billet fuel rails, Lucas 42 lb/hr injectors, an Aeromotive A1000 fuel pump and regulator would also complement the new intake by providing a great deal more fuel in preparation for the new motor.
Similarly the GTO was fitted with a complete Stainless Works three-inch exhaust system with long tube headers. Naturally aspirated the Goat gained 44 horsepower, but with the new jets not dialed in it ran 11.23 at 121mph with only a 1.63 sixty-foot before the stock posi gave out. Brett then made up his mind that instead of just replacing the posi, he would install a new differential that would be substantially stronger. In the interim, BMR made a redneck spool with spider gears and a TIG welder to enable one last run on the old motor. Right off the trailer it went 10.98 at 125mph, and shortly after joining the ten-second club burned a sizable hole in one of the pistons.
Right about now the six liter iron block Brett had purchased was coming back from A&S Motorsports in Riverview, Florida. This local machine shop was commissioned by BMR to bore .030 over and line hone the block before installing a host of top quality internals. The new bottom end would consist of Carrillo connecting rods, BRC custom pistons, and a Lunati 4340-forged, 4-inch crank to increase displacement to 408 cubic inches. An SLP ported oil pump and ARP main studs would also do their job in holding the new shortblock together.
Responsible for making the power would be a set of Stage 3 ported LS6 heads from CNC Cylinder Heads in St Petersburg, Florida and a custom nitrous cam measuring 0.595/0.601-inch lift, 232/236-degree duration at 0.050 and 113 LSA from Comp Cams. Unfortunately the new motor weighed over a hundred pounds more than stock and it was hard to justify that with only 414 horsepower at the wheels. The car was now running consistent 10.50s and cutting 1.55 short times, but still shy of the mark.
There was only one thing left to do, crank up the juice. The jetting once again went up and a NOS Progressive Nitrous Controller was also thrown into the mix to contain the juiced beast, allowing the system to back off on the initial hit. When combined with some lighter, stickier rolling stock (Bogart 15-inch wheels with Kuhmo skinnies and Mickey Thompson drag radials to be exact) the Goat pulled a 1.46 sixty-foot time on the way to 10.23 at 133 mph at the Thunder Shootout in November.
Alas the time had finally come for the nine, the nine-inch rear that is. In the affordable realm there was only one option, the Diff Technics Ford 9-inch replacement differential. While completely compatible with the rest of the IRS components, the larger center section could use the ring, pinion and posi of any other 9-inch. This made finding parts rather easy, as BMR was already a Moser distributor. Staying true to the previous formula, 3.50 gears were used with a Detroit Locker. Also the adapter was no longer needed on the driveshaft, making the previous unit two inches too short. This was the perfect opportunity to upgrade to BMR's 3.5-inch aluminum driveshaft rated to 900 hp and 7200 rpm. The larger differential required a new routing of the exhaust, and BMR decided to switch to Borla XR1 mufflers placed just behind the rear bumper on both sides.
On its first run on the track with the new differential and driveshaft the Goat managed to break the one piece on the entire drivetrain that was OEM. The outer axle stubs sheared completely off, leaving nothing to connect the axles to the wheels except the brakes. Once this unit is replaced with billet, there will be little to stop BMR's Goat from running nines--and being far out of reach of the next fastest GTO in the country.