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.
The Dynatech header kits come with a provision for the EGR fittings used in the '00 model cars. There's a small, brass pipe plug in the center of the header's EGR flange that has to be removed and dumped for the '00 cars. The plug remains in place on all other model years.
We slipped individual headers into the engine bay from the bottom of the vehicle and had a helper slide the kit-supplied gaskets into place and start a couple of the bolts on each after giving the threads a little dab of antiseize. Make sure your helper sets the proper gasket orientation, because getting it wrong at this point will create clearance issues with the spark plugs. We cinched all the bolts to 18 lb-ft and then reinstalled the spark plugs on the driver side.
Next we lowered the car and reassembled everything we disconnected under the hood. Once that task was complete, we moved back under the car and removed the factory exhaust hanger bracket from the transmission and put it into the parts box with the rest of the stock system. It won't be reused and there's no need to leave it hanging there.
The next step was to slip the two 3-inch doughnut gaskets over the end of each collector, making sure the flat side of the doughnut was pushed tight against the collector stop ring. The two PowerCAT converters were lightly bolted into position at the ends of the collectors.
We put a new clamp on the Dynatech Y-pipe and slipped it into the inlet of the stock tailpipe. We grabbed the passenger-side exhaust tube and slipped it into the converter and Y-pipe, repeating the procedure for the driver side.
Now that everything was in place, we swung the sheetmetal crossbrace back into position and secured it using the factory bolts. Kit-supplied band clamps were then positioned over all the joints in the new system and snugged. Working from the rear of the car forward, all the clamps were tightened, making sure the new pipes didn't interfere with any underbody components. We applied a tiny dab of antiseize compound to the threads of all four oxygen sensors and installed them into the new system. The rear sensors were fitted with the new pigtails included in the kit. We used the kit-supplied tie-wraps to secure the sensor leads away from the headers and clear of all the moving parts.
We checked the installation to make sure we didn't miss anything and then fired up the car to check for leaks. We also checked to make sure the "check engine" light didn't come on. Dynatech said some models will record a slow heat response or temperature error that will set off the "check engine" light. The company said this has no adverse effect on the operation or performance of the engine, but it can be annoying.A quick tweak of the ECU parameters with software such as LS-1 Edit or similar can shut off the light for good.
After making sure we were leak-free and weren't getting any untoward illumination on the dash, we jumped in and drove back to Willy's Carb & Dyno Shop to see what kind of improvement the new header system gave the Pontiac. We strapped the car to the dyno and made a few pulls. The addition of the Dynatech system racked up 348 peak rear-wheel horsepower at 5,700 rpm and 359 lb-ft of torque at 4,300 rpm, an increase of more than 20 rwhp and 13 lb-ft of torque.
| ||Base ||Base ||Mod. ||Mod. ||Diff ||Diff. |
|RPM ||TQ ||HP ||TQ ||HP ||TQ ||HP |
|2,700 ||328 ||168 ||335 ||172 || 7 || 4 |
|2,900 ||328 ||181 ||337 ||186 || 9 || 5 |
|3,100 ||331 ||195 ||343 ||202 ||12 || 7 |
|3,300 ||332 ||209 ||348 ||218 ||16 || 9 |
|3,500 ||334 ||223 ||350 ||233 ||16 ||10 |
|3,700 ||338 ||238 ||351 ||248 ||13 ||10 |
|3,900 ||342 ||254 ||356 ||264 ||14 ||10 |
|4,100 ||346 ||270 ||357 ||279 ||11 || 9 |
|4,300 ||346 ||283 ||359 ||294 ||13 ||11 |
|4,500 ||346 ||296 ||359 ||307 ||13 ||11 |
|4,700 ||341 ||305 ||358 ||320 ||17 ||15 |
|4,900 ||338 ||315 ||356 ||332 ||18 ||17 |
|5,100 ||334 ||325 ||351 ||340 ||17 ||15 |
|5,300 ||325 ||328 ||344 ||347 ||19 ||19 |
|5,500 ||313 ||328 ||332 ||348 ||19 ||20 |
|5,700 ||301 ||326 ||321 ||348 ||20 ||22 |
|Parts List |
|Component ||PN ||Price |
|Complete header kit, '98-'99 F-car ||115-732300S ||$1,295 |
|Complete header kit, '00-up F-car ||115-732325S ||1,295 |
|Headers, 131/44 , '98-'99 F-car ||115-732300 ||975 |
|Headers, 131/44, '00-up F-car ||115-732325 ||975 |
|PowerCAT converter, 2.250 ||79-400225 ||150 |
|PowerCAT converter, 2.500 ||79-400250 ||150 |
|PowerCAT converter, 3.000 ||79-400300 ||150 |
|Gasket set, stainless steel, LS1 ||61-30000S ||39 |