pypesleadartIf you’re like most car guys, the way your ride sounds is without question one of its most important features. Up there with its appearance and performance, your car’s voice is likely to be at the top of your list of priorities when it comes to tuning the car to your particular tastes. And, as many can attest, changing its sound can definitely turn it into a whole new animal.

Of course, short of modifying or swapping the engine, the exhaust system is really the only way to alter your car’s sound. There are countless different exhaust systems, components and alterations available, with each having its own effect on the noise. But while exhaust modifications do change volume and tone, noise is not the only thing affected – exhaust flow and consequently performance are changed as well.

We went to Pypes Exhaust for a system to equip a 1967 Chevelle with both a killer sound and superior performance. The Chevelle boasts a no-frills 427 cubic-inch big-block Chevy – carbureted, naturally aspirated, and with its original cast-iron heads and solid-lifters. But this power plant – old-fashioned though it may be – is certainly no slouch, providing the stout machine putting out around 450 at the rear wheels.

Previously, it was a dedicated drag car and had almost no exhaust system at all – simply turndowns off the header collectors. However, the owner decided he wanted his monstrous machine to have mild street-manners as well.

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A quality exhaust system makes all the difference in the world – every last bend counts.

Our Pypes Exhaust System

To give the Chevelle the desired exhaust flow and sound, we gave it a full, cutout-equipped exhaust system. While the owner wanted to make the car street-friendly, he also wanted to maintain the high-flowing exhaust capabilities – which made the car a perfect candidate for an electric cutout setup.

The Chevelle's New System

Full-kit mock up.

  • ’64  to ’77 A-Body three-inch crossmember-back exhaust system with X-pipe and Race Pro mufflers (PN SGA14R)
  • Three-inch dual-exhaust electric cutout kit (PN HVE10)
  • 3.5-inch header to three-inch pipe collector reducers (PN PVR13S)

Pypes Exhaust supplied the system; we got our hands on their 3-inch full exhaust, X-pipe system and dual-exhaust electric cutout kit. We got the chance to talk with Joe Gallen from Pypes Exhaust about the system as a whole, and he told us that the piping and mufflers are composed of 16-gauge, mandrel-bent, 409 stainless steel and the collector reducer and tips are polished 304 stainless steel.

The use of stainless steel means that no protective coating is required. Gallen said, “The stainless construction of our pipes and mufflers enables them to resist corrosion and extends the life of the system.” The mandrel-bent feature also ensures peak performance, due to the fact that mandrel-bent systems flow far more efficiently than compression-bent alternatives. So in regards to both durability and efficiency, the Chevelle’s exhaust system was going to be well-off.

To complement the system and tailor the sound to our taste, we also ordered a pair of Pypes’ RacePro mufflers. Three different muffler variations are offered –the Street Pro, Race Pro and Violator – and all are available to add to any Pypes system. Of the three, the Race Pro muffler we selected offers the best flow and the quietest sound rating. Upon hearing it on this Chevelle, though, you’d never believe it was the quietest – it utilizes a straight-through design (responsible for the high flow-rating) that issues a sinister, dominating tone.

'Straight-through' is meant quite literally.

Installation of the System

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Thanks to the stainless steel that it’s made from, you’ll never have to worry about your Pypes system rusting over.

Along with the main components, the system also comes complete with all the hardware and accessories you’d need – tailpipes, clamps, hangers, and of course, the all-important instructions. While it goes strongly against typical-gearhead procedure, be sure to read the instructions before hastily throwing all the shiny new pipe on your car. By doing so, you’ll learn that the install needs to move from the back of the car towards the front, counter-intuitive though it may be.

Pypes Install 33Ensuring that we observed this, our install went like clockwork. Gallen explained to us that this install simplicity was one of Pypes’ main goals. He stated that “all of Pypes’ kits are designed for the home builder to easily install using basic hand tools”.

The only thing preventing us from simply bolting the system into the Chevelle was the layout of its Chevy big-block. The engine has a layout that causes one bank’s header tubes and collector to sit a bit further back than the other’s. As a result, the post-collector piping of that bank also sits a little further back than the other.

However, Pypes takes variables such as this into account by providing more than enough tubing to accommodate different setups. The offset collector piping was easily remedied by trimming just a few inches off of the foreword-most collector.

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Notice the offset lengths of the collector tubing, due to the varied header lengths.

After trimming, the extending pipe lined up beautifully.

With most aftermarket exhaust installs, some amount of modification is required, such as trimming excess pipe or patching in more to fill gaps. With ours, all we required was cutting down the one collector and everything else fit like a glove. Essentially, if you’re able to get your car up off the ground, you can crawl right under and get your kit hooked up with little to no hassle.

Scavenging And Exhaust SystemsPypes Install 44When it comes to your ride’s performance, why is the exhaust system so crucial? Well, different systems will offer different exhaust flow characteristics, depending on tubing size, length, the number and type of bends, and so on.

The internal combustion engine acts as an air pump, depending on efficient air and exhaust flow to operate properly. Obviously, exhaust flow is the name of the game – the more efficient the exhaust flow, the better. But while it’s a topic of great confusion for many, back-pressure is, in fact, crucial to an exhaust system, as it can both improve or limit performance.

To achieve the most efficient flow, a certain amount of back-pressure is required; too much or too little can create problems. Too much back-pressure and exhaust gas velocity (flow speed) is decreased, reducing the scavenging effect that’s crucial to efficient exhaust gas extraction. Too little back-pressure, and the same result is achieved – exhaust gas velocity and scavenging are both reduced.

To achieve the greatest scavenging effect (and consequently the greatest performance), optimally-sized exhaust tubing must be used. And of course, what determines ‘optimal’ will vary depending on the engine. For example, cars putting out around 200-300 horsepower will work best with something like a 2.5-inch pipe diameter. Cars closer to the 400-and-up mark will perform best with 3-inch or larger systems.

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Putting down around 450 ponies, this Chevelle is obviously worthy of its 3-inch exhaust piping.

The shape and design of the exhaust system also plays a part in both performance and sound. Since exhaust flow is what you’re after, the straighter the system the better. Obviously, a straight-piped system will be more beneficial; at the other end of the spectrum, however, are systems – typically from the factory – with all sorts of bends, turns and other restrictions (i.e., mufflers and resonators).

But for lower horsepower cars, this restricted exhaust system provides the necessary back-pressure for the engine. Put a straight-piped system on a 200-horsepower car and you will not necessarily see a power increase.Pypes Install 22High-horsepower cars, in that 400-and-up range, are another story. For these cars, low-restriction, straight-piped systems typically are beneficial. But other than the obvious performance deficit between a factory system and a straight-piped system, the major difference between the two is, of course, the noise.

If you’ve ever experienced the awesome terror of a straight-piped V8 up close, then you’ll understand why it’s not quite legal on public roads. While a muffler-free, straight dump system can offer superior performance, the noise-level is far too overbearing for just about anywhere but the track.

Exhaust Cutouts

Suppose, however, that you’d like to use your thunderous drag car or track-machine – which you want the greatest possible exhaust flow from – as a weekend cruiser from time to time. To avoid the headache of swapping your entire exhaust system between street and track, the ever-inventive gearhead community came up with cutouts.

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The short leg of the Y (the cutout itself) typically has a three-bolt pattern where either an immobile block plate or electrically motorized valve is mounted.

Exhaust cutouts have been around for quite some time, and the concept and design have not changed much. The theory behind this is simply to provide a way to quickly transition from a free-flowing, earth-shaking system to a more quiet, street-friendly alternative.

This is accomplished with a Y-joint placed in the exhaust system (before the mufflers, of course). One leg of the Y-joint sends exhaust gases to the muffler, whereas the other bypasses the mufflers, resonators, and remainder of the exhaust.

Exhaust gases, much like water or electricity, will always take the path of least resistance. When the cutouts are closed, the gases have no escape except the end of the tailpipe; when they are open, however, the cutout becomes the shortest and easiest path for the gases to flow. The cutout dumps the exhaust straight out, with little to none traveling through the full system.

Our Pypes electric cutouts sit perfectly in the system to allow maximum flow when the cutout valve is opened.

By bypassing the various bends, resonators and mufflers in the full system, cutouts provide a much shorter and more direct path from exhaust to escape – drastically improving flow. The quick and easy transition from quiet and restricted, to fast and loud, make cutouts especially useful for cars that frequent the track and the strip, and maybe for a little showboating here and there.

But when it comes to cutouts, what you’ll find in many different setups is that the cutouts focus on the showboating part – they increase noise, but don’t do much for performance.

exhaust flow diagram

On the left, a setup that does not flow exhaust towards cutout; on the right, the setup aims exhaust directly towards cutout, as in our Pypes kit.

As you can see in the illustration, this type of design (as show on the left in the above image) does not force the exhaust out of the cutout; with the exhaust flowing through the leg of the Y that’s inline with the full exhaust system, the effects of the cutout are minimized.

There is a definite difference between the two types of cutouts, ours is designed for power increases in a performance application and the other is more for showing off. -Joe Gallen, Pypes Exhaust

More performance-minded cutout kits, however (illustrated by the design on the right), are set inline with the X-pipe. Exhaust is directed straight towards the cutout opening, so flow is optimized for the setup. This is the design that Pypes Exhaust uses for their cutouts, and consequently what we placed on the Chevelle.

Gallen told us, “There are two main benefits we want to establish for the two types of people who would purchase our cutouts. For the weekend racer who drives and enjoys his car during the week and then takes it to the track on weekends, and street driven cars that want to ‘shock or impress’ people at a traffic light.”

He continued, “There is a definite difference between the two types of cutouts, ours is designed for power increases in a performance application and the other is more for showing off.

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Cutouts are a great way to give your hopelessly-loud drag car the quiet it needs to frequent the streets.

Conclusion

All in all, the exhaust was a pleasure to install and is now even more of a pleasure to listen to. As Gallen put it, “Pypes Exhaust systems as a whole come with many benefits: we use 100 percent stainless steel for longevity, they’re X-pipe based and mandrel-bent for performance, people can tailor sound with our three choices of mufflers … and at the end of the day, a price the average buyer can afford.”

Prior to the cutout install, the Chevelle was mind-numbingly loud at all times. Now however, the owner proclaimed that – with the mellowed note of the closed cutouts – he can finally hear himself think while driving his car. The Pypes system sounds incredible, looks just as good, and, thanks to the kickass electric cutouts, can provide both killer performance and streetable sound.

If you find yourself at the crossroads of wanting superior performance, but also maximum streetability, visit the Pypes Exhaust website and check out its systems for your application.