Aftermarket Parts - Are Premium Parts Worth The Price?

We made one quick test where we looked at the effect of tailpipes on the 3-inch system. Ironically, the tailpipes improved peak power by 1 hp but lost torque big-time down low and in the middle compared to no tailpipes on the 3-inch system with the engine making 470 lb-ft of torque.

211/42- Vs. 3-Inch Exhaust
What goes in has to go out with any high-horsepower street combination, but for many car builders the question of what to do with the exhaust system is often given afterthought status. For professional engine builders and those attuned to the needs of an engine that moves trainloads of air, exhaust systems can make or break the combination. It's acknowledged that exhaust systems don't make horsepower, but a poorly executed exhaust system can cost too much to be blatantly ignored. There are still those who feel that open exhaust is the only avenue to peak horsepower success, and we won't argue the point. But the reality is that a properly designed exhaust system can minimize the power loss and perhaps even pump up the torque at the same time.

Our test was devised to be as simple as possible: to compare 211/42-inch versus 3-inch-diameter Flowmaster Super 44 mufflers.. There are plenty of 3-inch exhaust systems out there designed to fit many popular musclecar chassis intended for big-cubic-inch engine applications. The engine combination for this test began with the 383ci small-block, with the larger Dart 227 CNC ported heads and the big XR292 Xtreme Energy roller cam combined with the Holley-Dorton intake and 750 Street HP carburetor. Instead of the 131/44 custom dyno headers, we substituted a set of Hedman 131/44-inch chassis headers that offered a three-bolt flange to install the 211/42- and 3-inch exhaust pipes. While the 3-inch system looks massive and flows lots of air, if you are considering one of these systems, the big concern should be sound level. It is inevitable that a 3-inch exhaust will also be the loudest. The large flow area of the 3-inch system represents a 45 percent increase in area, which means the mufflers and tailpipes create a resonance that can be overwhelming, in much the same way that big exhaust tips on import cars resonate (except not as annoying). But beyond the noise factor, there is definitely torque and horsepower to be gained with a 3-inch exhaust system, and we wanted to know how much on our 500 hp 383 small-block.

The muffler we chose to test is the new Flowmaster two-chamber, Super 44 muffler in a 4-inch case. This is Flowmaster's most aggressive muffler, so we're really putting the sound level to the test. The top muffler is a 2 11/42-inch while the bottom is the more aggressive 3-inch. According to Flowmaster's Kevin McClelland, minimizing the offset between the muffler's inlet and outlet improves power.

It was interesting that at the peaks the 2.5-inch mufflers were barely 5 hp shy of the 3-inch ones, but that's not even half the story. Looking at the entire curve, the 3-inch system delivers substantially more torque virtually throughout the 2,700- 6,500 test sweep. This may be more of a tuning issue than just a question of volume, but there's no questioning the solid 11 hp gain the 3-inch system delivers between 5,100 and 5,700 rpm. That's power that will show up on the e.t. slip every time. While we didn't itemize the power numbers on the chart, we also threw on a pair of 3-inch tailpipes on the 3-inch mufflers. Surprisingly, the tailpipes actually delivered a tiny 1hp gain at 6,500 rpm with 510 hp, but again, looking at the entire curve, the tailpipes cost power almost throughout the entire pull, losing as much as 32 lb-ft of torque at 3,300 rpm. Using an average power evaluation, the tailpipes lost exactly 9 lb-ft of torque and 6.4 hp overall, so clearly tailpipes cost some power, although not at all where you might expect. It's also possible that carburetor tuning might be able to make up some of this torque loss. Another interesting test would be to add an H- or X-pipe to this test and see what occurs. But that will have to wait for another day. We've burned our hands enough times during this test already.

Flowmaster 211/42- Vs. 3-Inch Mufflers
The first test is the baseline, with a pair of Hedman 131/44-inch headers connected to a complete 211/42-inch exhaust system with the Flowmaster Super 44 mufflers and no tailpipes. The second test upgraded to 3-inch inlet and outlet Super 44 mufflers.