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Big Power Gains For Your LS1Exhalation Therapy From the April, 2009 issue of Corvette Fever Photography by Dave Emanuel
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Now that the LS1 engine has proven itself to be the best-performing pushrod engine ever built, it seems ludicrous that its power-producing capability was ever doubted. And to add insult to the injury suffered by the doubters, the LS1 has also demonstrated that it maintains the tradition of its predecessor in responding enthusiastically to performance-enhancing modifications. One of the easiest-and most rewarding-LS1 modifications is the installation of headers combined with an exhaust-system upgrade. Specifically, a set of TPI Specialties long-tube headers combined with a Random Technology stainless steel 3-inch converter/X-pipe assembly and exhaust system, bumped the peak rear-wheel horsepower of a stock '01 roadster from 297 to 337-an increase of 40 hp. On the Speed Hound Performance... On the Speed Hound Performance dyno, this '01 roadster registered an increase of 40 hp and 33 lb-ft of torque following installation of TPIS headers, and a Random Technology converter/X-pipe assembly and converter-back exhaust system. According to Corvette specialist Jody Gregg of Speed Hound Performance, "Installing headers and an exhaust system on a C5 is relatively easy-especially with this combination of equipment. Everything bolts together so there's no welding or fabrication involved. And as the dyno numbers show, you get a big increase in power across a pretty wide rpm range." When you compare the numbers, you see that from 3,700 to 4,400 rpm the increase is over 20 hp; from 4,500 to 5,200 the increase is over 30 hp; and from 5,300 to 6,000 the increase is over 40 hp. Keep in mind that this is a stock engine. The increases would be even greater if internal modifications had been made or a supercharger had been installed. Although you'll find any number of advertisements claiming that a few minor tweaks will deliver "massive" power gains, in the real world a 10 percent boost in power isn't easily achieved. As is the case with the engine itself, the key lies in the overall combination of components. Individually, headers, high-flow catalytic converters, and a low-restriction converter-back exhaust system will all deliver measurable gains. But when the right parts are combined, the whole equals more than the sum of the parts. However, since not all C5 owners may want to install long-tube headers, Random Technology offers converter/X-pipe assemblies to fit stock exhaust manifolds and shorty headers. The company has also developed a 3-inch converter/X-pipe assembly, and a matching 3-inch converter-back exhaust system. This system is designed for maximum output applications, but has proven to be worth a few horsepower on a stock engine. As the accompanying photos illustrate, installation of all components is fairly routine and can be accomplished by anyone with a reasonable amount of wrench-turning experience. If you decide to do the installation yourself and haven't worked on a C5 before, keep in mind that the LS1 is a "metric engine," requiring-you guessed it-metric tools. Also, check your local emissions legislation to ensure compliance with local requirements.  Just as the knee bone is connected...  Just as the knee bone is connected to the shin bone and the shin bone is connected to the ankle bone, the exhaust system is connected to the H-pipe and the H-pipe is connected to the manifolds. Before any of these subassemblies can be removed, they have to be disconnected from each other. But before unbolting any of the system...  -...the rear oxygen sensors...  -...the rear oxygen sensors should be removed. The sensors screw into the H-pipe behind the catalytic converters, but the harness attached to them runs forward and is attached to the heat shield with a series of clips. After disconnecting the connectors from the car harness, the clips should be pulled from the heat shield.  After all the clips are removed,...  After all the clips are removed, pull the harness loose.  Next, remove the oxygen sensors...  Next, remove the oxygen sensors from the H-pipe with a 7/8-inch open-end wrench or an oxygen-sensor socket.  The first fasteners to be...  The first fasteners to be removed are the bolts that hold the H-pipe to the exhaust system.  Next, the three nuts that...  Next, the three nuts that hold the front of the H-pipe to the exhaust manifolds should be loosened, but not removed.  The bolts that hold the front...  The bolts that hold the front H-pipe bracket to the bellhousing are the next to go. When they're removed, the front of the H-pipe will drop down on the manifold nuts, which is the reason they should be loosened, but not removed.  Two bolts hold the assembly...  Two bolts hold the assembly to the rear hanger. When these are removed, the only fasteners holding the H-pipe in place are the nuts on the exhaust-manifold studs. With the manifold nuts loosened, the rear of the H-pipe may be lowered onto the ground or a support. Then remove the nuts on the manifold studs, lower the H-pipe/converter assembly, and slide it out from beneath the car. Since the H-pipe is over 6 feet long, it's a good idea to have an assistant help with its removal.  $^p<$E?re ready to tackle...  $^p<$E?re ready to tackle exhaust manifold removal. The driver side is the more complicated of the two because components like the steering shaft are in the way. Remove the bolt that holds the shaft to the steering box and slide the shaft out of the way.  Then remove the coil covers,...  Then remove the coil covers, alternator, and the bolts that hold the coil assembly to the valve cover.  Once all the bolts are unbolted...  Once all the bolts are unbolted and the connectors disconnected, the coil assembly may be lifted out of the way.  Next the fuel line can be...  Next the fuel line can be disconnected; but before removing this clip, make sure pressure within the system has been bled off. It's also advisable to loosen the gas cap to relieve any pressure that may have built up in the tank. Leave the cap just loose enough to allow pressure to bleed off, until the gas line is reconnected.  Special plastic clips, available...  Special plastic clips, available through auto parts stores or fuel-injection specialists, are required to pop the fuel line off the fuel rail.  Now the bolts that hold the...  Now the bolts that hold the manifolds to the head can be removed and the manifold lifted out of the engine compartment.  There isn't much in the way...  There isn't much in the way on the passenger side, so once the coil assembly is removed, the manifold can be unbolted...  ...and extracted from the...  ...and extracted from the engine compartment.  Next the headers can be worked...  Next the headers can be worked into place. It may look like a difficult task since the collectors twist around, but TPI Specialties did an excellent job of designing the headers and they are surprisingly easy to work into position.  After the driver-side header...  After the driver-side header is in position, start two bolts to hold it in place, but don't tighten them.  Next, lower the passenger-side...  Next, lower the passenger-side header into place and thread a couple of bolts loosely into the head.  The headers connect to the...  The headers connect to the same mounting bracket as the front of the stock H-pipe. Leaving the header bolts loose allows the headers to be easily positioned to facilitate installation of the hanger bolts.  Once the hanger bolts have...  Once the hanger bolts have been started, the driver-side header bolts can be tightened.  Then the passenger-side header...  Then the passenger-side header bolts can be snugged and the hanger bolts tightened.  Next, it's time to reconnect...  Next, it's time to reconnect the steering shaft...  ...and slip the fuel line...  ...and slip the fuel line onto the fuel rail and reattach the retaining clip.  Finish up by reinstalling...  Finish up by reinstalling the alternator, emissions equipment, and coil pack.  With the headers in place,...  With the headers in place, the Random Technology converter/X-pipe assembly can be installed. Part number 752722 is designed specifically to fit C5s with TPI Specialties headers, so installation is easy. Other models are available to fit stock exhaust manifolds.  After installing the oxygen...  After installing the oxygen sensor in the converters, they can be slipped into the header collectors.  Then the X-section can be...  Then the X-section can be slid onto the converters, lifted up into place and bolted to the exhaust system.  After the rear hanger bolts...  After the rear hanger bolts are installed and all connections tightened, you're ready for a testdrive.  TPIS long-tube headers feature...  TPIS long-tube headers feature 1 3/4-inch-diameter primary tubes, all the required emissions-control connections, and metallic/ceramic coating.
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