One of the best bang-for-the-buck modifications anyone can make to any stock vehicle is to open up the exhaust by replacing the stock manifolds with headers. Sure, getting more air into the engine can contribute some power gains. But those will be minimized if the back door is clogged with restrictive pipes.
The idea behind a good header system is to make it easier for the engine to squirt the exhaust gases out of its cylinders by eliminating the backpressure inherent in the stock manifolds. When the headers are properly designed, each cylinder gets its own equal-length pipe, which sends the exhaust gases to the collector in equally spaced pulses, so no backpressure is created by all the cylinders trying to stuff their gases into the exhaust pipe at once.
This kind of stuff is car crafting at its most basic, but it never hurts to prove the old saw with some fresh hands-on testing. We lined up a vehicle-an '02 Pontiac Trans Am WS6 fitted with Flowmaster 40-series mufflers, a velocity stack in the throttle-body, and a K&N filter-and arranged for the folks at Dynatech Competition Exhaust Systems in Boonville, Indiana, to install one of its new SuperMAXX F-Body header systems. Featuring CAD-designed Type 304 stainless-steel construction with CNC-machined flanges, mandrel-bent tubes, and the company's high-flow PowerCAT catalytic converters, Dynatech says the system should increase exhaust flow from our Poncho by almost 47 percent.
We don't generally take such statements at face value, so we pulled the car onto the Dynojet chassis dynamometer at Willy's Carburetor and Dyno Shop in Mt. Carmel, Illinois, and made a few pulls. The best of the bunch before the header installation netted us a respectable 328 peak rear-wheel horsepower at 5,500 rpm and 346 lb-ft of grunt at 4,100 rpm. Then we took the car back to the Dynatech shop where we installed the company's new SuperMAXX header system to see whether the extra-long, 131/44-inch primary tubes with the company's PowerCAT catalytic converters would make a difference in the car's performance.
Installation started under the hood of the car where we disconnected the battery and removed a pair of 8mm bolts from the air-tube flanges on either side of the engine before propping the steel lines out of the way. Then we pulled the spark-plug wires and removed the plugs from the driver side of the engine and unbolted the dipstick tube bracket so we could remove the whole assembly.
Moving to the underside of the car, we got busy with a ratchet and removed three of the four bolts holding the small sheetmetal crossbrace to the bottom of the car. The fourth bolt was loosened enough to allow us to swing the crossbrace out of the way.
The clamp nuts and bolts were removed, as was the clamp holding the tailpipe to the factory exhaust pipe. We also pulled the bolts holding the two flange clamps at the rear of the stock converters. At this point, it was a simple matter of separating the factory Y-pipe from the converters and the tailpipe and dropping it from the car.
All four of the car's oxygen sensors were removed from the stock system and temporarily left hanging. Longer, kit-supplied pigtails will be installed later to accommodate their new mounting positions in the header system. We then removed the bolts holding the catalytic converters to the cast factory manifolds and yanked the cats.
Getting out the factory exhaust manifolds requires a little effort. First, the rearmost bolts on each side are easiest to get to from underneath the car. We went topside to remove the remaining manifold bolts, raised the lift again, and dropped the stock manifolds and gaskets out of the car. The Dynatech headers are installed from underneath.