Y-pipe-to-transmission crossmember-bolts...
Y-pipe-to-transmission crossmember-bolts are taken out and the Y-pipe is separated from the after-cat junction by gently tapping it toward the front of the vehicle and twisting until it comes free. The Y-pipe is lowered and a 7/8-inch wrench removes the four O2 sensors from the catalytic converters and exhaust manifolds.
Conclusion
After the installation and dyno testing concluded, the '00 T/A gained 25.8 rear-wheel horsepower and 21.6 lb-ft of torque at the peaks. Although peak horsepower and torque are important, the best gauge of the effectiveness of the changes is reflected in the average power gains. Mathematically, the numbers show average gains of 19 and 20 rwhp and torque gains respectively, but by themselves the numbers don't tell the whole tale.
Baker states, "Power has been significantly increased from off-idle to the redline. Although I was worried that large primary, long-tube headers might decrease power in the lower rpm range, those worries were quickly put to rest on the testdrive home. Having a system that has the ability to support both the EGR and AIR valves on the header itself was important. There are a few manufacturers that offer long-tube headers featuring the Y-pipe and test pipe/catalytic converter design that allow the car to be emissions-legal with a few turns of a socket wrench. Overall, the quality of the system and the header/Y-pipe clearance are excellent."
The car is then lowered, the...
The car is then lowered, the aftermarket strut tower brace is removed, and the EGR valve's wiring harness is disconnected before the two 10mm bolts that mount the EGR valve to the cylinder head-mounted bracket are unbolted.
According to Brian Lohse, co-owner of RPM, "We have installed Jet-Hot headers on several F-bodies and one of our employees has them on his 10-second Trans Am. The headers fit well and the Sterling finish coating has proven to be very durable, even under race conditions. The headers, Y-pipe and intake manifold swap produced good power, but another 5-10 rwhp could have been gained with a custom tune. Since the car was scheduled for a camshaft swap the next weekend, tuning would take place then instead, as a higher duration and lift cam requires a custom tune as well. The best indicator of the power capabilities of the car will occur when the cam is installed and the engine is tuned to its potential. If, for example, we had first installed the camshaft and a custom tune before upgrading to the Jet-Hot headers and the SLP LS6 intake, the test results would likely indicate that the headers and intake yielded greater gains. Rather than focusing on trying to maximize this portion of the test, we will concentrate on the total power package and optimize the combination after the camshaft is installed."
By increasing the airflow into the motor and freeing up the exhaust system, this T/A is primed and ready to take the next leap forward in power. Stay tuned for Part II when we install a Comp cam and related valvetrain hardware to turn this car into a "cam-only" missile.
Dyno Testing & Results
Testing of the WS6 '00 Trans Am was performed at Real Performance Motorsports (RPM) in Lewisville, Texas. RPM has a Dynojet Model 248C dyno capable of measuring up to 1,200 horsepower and is optioned with the above-ground kit and the Commander wide-band 02 sensor so air/fuel ratios can be charted.
The barometric pressure, air-inlet temperature and SAE correction factors for the runs are listed below. Correction factors use a standardized SAE calculation, which include reference temperatures of 77 degrees F, and a barometric pressure of 29.23 inches of mercury.
Key engine parameters: air-inlet temperature (AIT). Maximum values are noted unless otherwise stated. Peak and average horsepower and torque are dyno pulls recorded between 3,800 and 5,800 rpm.