2002 Chevy Truck Exhaust - Going With The Flow

When we last left you, we had added a free-flowing cold-air intake and mass airflow sensor (MAF) on our '02 Chevy truck. Well, now we can get air into the engine, but that stock exhaust is a bit restrictive. To get rid of some back pressure and add additional horsepower we called on the pros at Magnaflow to set us up with the appropriate exhaust system for our daily driven truck. Magnaflow's solution came in the form of an after-cat system built entirely of stainless steel. For that added "bling," the muffler is even polished! Well, that won't give us any additional horsepower, but it sure looks great, and with the polished stainless steel tip it will provide us with an exhaust system that is very corrosion resistant and that will possibly outlast the truck.

The truck's original exhaust... 

   

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The truck's original exhaust isn't much to look at and is very restrictive and heavy-we will fix that! We started by removing the rubber mounts from the original exhaust. Be sure to leave the rubber mounts on the body; we will use these to mount the new Magnaflow system.

Our first step was to strap our truck down on the Dynojet 248 and get a baseline, so we were off to the Primedia Tech Center where we produced a base 228.1 SAE corrected horsepower, with 276.5 lb-ft of torque. Satisfied with a reliable and consistent baseline, it was onto our Autolifters lift, where we started removing our old, restrictive stock exhaust. This is a simple job that is much easier on a lift but can be performed in your driveway. We started by unbolting the fasteners that go into the catalytic converter and prying the rubber mounts off the hangers mounted on the original exhaust. Be sure to leave the rubber mounts in place on the truck, as they will be reused. Starting at the front by the catalytic converter, we attached our first pipe, then snaked the rear tailpipe in place and mounted it on the rubber mounts. We did this so we could center the muffler and adjust the pipes so they won't rattle or rub any of our suspension components. When we were satisfied with the fit, we tightened everything and fired up the truck to check for exhaust leaks. Since the Magnaflow kit fits so well, we weren't shocked to find we had a nicely sealed system, with no leaks.

The exhaust note was considerably deeper, yet not obnoxious-very tolerable, even on a long trip. We figured it was time to see proof in numbers, so we strapped it back on the Dynojet. After three pulls, we came up with a best of 235.8 SAE corrected horsepower, with 281.2 lb-ft of torque; that's a 7hp gain and a 5-lb-ft gain in torque. Keep in mind these numbers reflect three runs of testing, and there is still more we can do to our truck to pick up some valuable horsepower and torque. However, for now, this makes our truck sound great and perform equally as well. Follow along and see how 30 minutes of work and one Magnaflow after-cat system can gain a few ponies and make that Chevy engine roar.

Evident in this photo is the...        read full caption Evident in this photo is the enormous size of the original muffler. We will replace it with the supplied polished stainless steel free-flowing Magnaflow muffler.	The new after-cat system looks...        read full caption The new after-cat system looks great, will be extremely durable for the life of our truck, and also rewarded us with the horsepower and torque gains we were looking for to complement our Granatelli MAF and cold-air system.	Only a couple of bolts attach...        read full caption Only a couple of bolts attach the old exhaust to the catalytic converter. With the help of our Craftsman impact gun, the bolts spun out and the old exhaust was removed.
Now it's time to install the...        read full caption Now it's time to install the new stainless steel Magnaflow system. We started at the front and attached the first pipe to the catalytic converter but didn't tighten the bolts yet.	Now, we snaked the tailpipe...        read full caption Now, we snaked the tailpipe and muffler in place...	...sliding the mounts welded...        read full caption ...sliding the mounts welded onto our tailpipe into the original rubber mounts; these support the tailpipe and muffler.
After checking all of our...        read full caption After checking all of our clearances, being sure nothing was going to rub or hit any of our suspension or body, we tightened everything down and checked for leaks. Total installation time was under 30 minutes. Now we have a great sounding exhaust that actually performs, and we have the dyno results to prove it!