Front and rear suspension modifications include Eibach springs installed for a total two-inch drop. Stock rear struts were retained with the addition of Monroe air adjustable shocks in the rear keep a consistent ride height when passengers are on board. Axis Hiro 19x8.5 fronts and 19x9.5 rears were mounted on Dunlop SP9000 tires. Staggered-sized 235/35/19 fronts and 275/35/19 rears were installed in order to achieve a rake that would let people know that the car was a rear-wheel driver.
The high ride quality, as good or better than OEM, is the successful combination of the Eibach springs and Dunlop SP9000 tires. In the owner's view, the Dunlops provide better ride quality than any other low profile tire on the market. Bigger front 13-inch Stainless Steel Brakes with slotted rotors and three piston aluminum calipers replaced the stock units. The stock rear disc brakes were deemed more than sufficient for excellent braking. The Tremec six-speed benefits from the SPEC Stage 3 hybrid clutch and billet flywheel. A factory limited slip differential spinning 3.42 gears provides an excellent performance/cruising combination.
What would it take to get an old 1970 GTO to make almost 500 hp at the wheels? It would take a stroker 455 with Edelbrock heads, a lumpy cam, and a big 850-cfm carburetor. Will a typical Chicago hot rodder get in that car and drive it to California? Not likely. That old school technology is going to get 8 mpg, idle at 1,250 rpm, and break valvetrain components. Though big on the wow factor, it would be driven occasionally, and be a chore to maintain reliability. Modern technology provides a better alternative.
Bill Hahn, owner of Hahn RaceCraft, a recognized leader in turbocharger systems for a broad range of vehicles, was on hand to discuss the Twin Turbo GTO:
"At Hahn Racecraft, we wanted to show the capabilities of the GM LS1 and LS2 drivetrains. We wanted to build this car with serious impact, a tour-de-force to demonstrate our capabilities with some very tasty design and execution. The goal was to maintain OEM level engineering from a twin turbocharged engine that would still maintain the daily driving civility of the car. We ended up with a car that puts 476 hp to the wheels at 7.5 lbs of boost with 93 octane gas. That power is achieved without internal engine modifications, on a car that retains its stock catalytic converters, and thus complete emissions legality.
"This GTO is an important car for Hahn Racecraft because we've been very impressed with the LS series GM engine, and see its massive potential in the years to come. We wanted to demonstrate what it can achieve with our unique flavor. While we have done custom V-8 turbocharging technology since the early 1990's, only as of late are we bringing V-8 turbo systems to the general public. This GTO had to show what we are capable of giving the customer in terms of design excellence and results. It's been a fabulous prototype for the next steps. We'll start with turnkey installations at our facility, and if demand permits, we'll then package the turbosystem to be sold and installed in the field."
The system's design criteria are evident from the first view. It has an OEM-yet-trick flavor, with every part purposeful. Extensive heat shielding is used to show off fabrication techniques and also provide a finished look. Note the lack of spark plug wires-they've been cleverly re-routed using ACCEL leads to clean up the appearance and protect them from heat.