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Flow to Go!

Ed Zinke Mar 16, 2005

While we can be guilty of extreme forward thinking and constantly looking for the latest and greatest trends, normally we tend to "go with the flow" by showcasing some of the fantastic rides that are built. However, in this case we have been given the opportunity to "flow to go" with some brand new products hitting the market from MagnaFlow Performance Exhaust and the Hooker Header division of Holley Performance Products. To prove the point that good non-restricted exhaust flow equals lots of get-up-and-go, we did a complete install and tested the results for each step in the process.

Our "test mule" was a totally bone-stock '64 Chevelle that's currently motivated by a 327ci small-block with old-school double-hump heads and a cast-iron intake breathing though a Carter four-barrel. It's certainly not a bastion of high performance, as about the only alteration on the car since its delivery 40 years ago was a dual exhaust system with almost three foot long glass packs--blown out of course. We backed the car into our Tech Center and strapped to the DynoJet for initial performance readings. It produced a whopping 147.2hp with 205.3 ft.-lbs. of torque. A street rocket it's not, but it does provide for an excellent starting point that many of us have had in our driveways at one time or another.

It's a given that getting good flow from your exhaust system is key to increasing the "go factor" of your ride. The other thing that needs to be kept in mind is pay attention to details during installation to insure a great fit under the car without rattles. Lots of combinations have been written about over the years, but it was a pretty slick opportunity that we had a chance to get dibs on some brand-new products from two outstanding companies in the performance aftermarket. MagnaFlow Performance Exhaust, well known for its high-performance exhaust systems predominately for late-model applications, is introducing a brand new system for musclecars called the Crossmember-Back Performance Exhaust System. In order to mate this new system to our small-block, we incorporated into the install the new Competition Series stainless steel headers from the Hooker Header division of Holley Performance Products.

Starting at the engine, we went to our trusted friends at Johns Customz in Torrance California for installation of the Hooker headers, which were a direct fit for our A-Body test mule. These new headers are made from mandrel-bent 304 series tumble finished stainless steel with 1 5/8-inch primary tubes and 3-inch long transition collectors that are designed to reduce back pressure and increase exhaust flow. The units come complete with collectors, gaskets and bolt kit for a broad range of applications. The installation itself isn't that difficult, although it does have its trying moments.

After removing the factory manifolds, the right bank header slid right into place with just a wiggle or two. The left side proved to be a bit more challenging, requiring the motor mount to be loosened and lifted slightly as we ducked and darted around the steering shaft, brake lines, automatic transmission linkage, and oil filter. We then hooked the current exhaust system to the headers and the car was back up on our DynoJet with an improvement of 6.8 percent with 157.2hp and 219.6 ft.-lbs. of torque. The car also produced a little different exhaust note and seemed to have a bit quicker throttle response.

MagnaFlow's new Crossmember-Back Exhaust System is a whole new foray into the musclecar market with a complete kit in a box. From all accounts they have done their homework and provided a great system that incorporates their Tru-X technology along with a host of added value. The main component of the system is their Tru-X center section pipe that is a combination of an X-style crossover and intermediate pipes. The Tru-X crossover is an improvement over conventional H-pipe balance tubes in that it improves exhaust scavenging by creating its own additional vacuum in the system to pull exhaust through while lowering decible levels.

The pipes in this system are mandrel bent 400-series stainless steel for superior strength and corrosion resistance. Mandrel bent pipes are far superior in that the interior of the pipe stays constant through the bend and less restrictive by as much as 20 percent over OE pipes. The highly-polished mufflers are a MagnaFlow standard item that has been engineered for the application. Their unique straight-through design from 16-gauge stainless steel is lined with both a special acoustical suppression material and stainless steel mesh to control noise and give an absolute superb exhaust note.

A great added feature with the Crossmember-Back system is that MagnaFlow provides three different exit points that owners can choose in their package: straight down off the mufflers, over the axle and to the side, or over the axle and straight out the back--which is what we choose. All clamps and hangers are included and to finish things off are two really cool highly-polished tips.

We went to MagnaFlow's fantastic Tech Facility where Jose Gonzales and Jim Gose laid their professional wrenching abilities on our Chevelle. The installation process was straightforward and given how well the system fits could be done at home on jack stands in less than a day. The pipes hug the floor plan of the car while providing adequate clearance to avoid rattles. The connector pipe to mate the system to any header application is provided with enough length and a 45-degree angle to allow for any offset in length or height variances, which our project had both.

The guys at MagnaFlow also told us we could easily take two to three degrees of timing out of the engine, but for consistency the final dyno run was done without doing any type of additional tuning. From our pulls the average horsepower was up to 165.25 and torque registered at 228.6 ft.-lbs. for an additional improvement of 5 percent.The combination proved solid increases in horsepower and torque on our mule. Overall power gains of 12.2 percent were realized with an additional 18hp and 23.2 ft.-lbs. of torque that you can feel. The exhaust note is so sweet and mellow it demands that you drive with the windows down or in our case with the top down.

So before you hang just any system under your next project, check out MagnaFlow's new Crossmember-Back Performance Exhaust systems today. Flow to go for real.


Here is our starting point bone stock small-block. From the air cleaner all the way to the exhaust manifolds and beyond it is pretty much as-delivered 40 years ago.

After removing the factory manifolds, John at Johns Customz chases the threads in the head as a precautionary measure.

With a relatively empty area the right bank headers slide in with minimal effort. Sufficient clearance is allowed so that you can run regular size spark plugs.

The left bank installation proved to be a bit more challenging as we needed to loosen the motor mount to lift the engine slightly. With that, things went pretty much as expected.

With the header in place we used a combination of the provided bracket and the factory alternator bracket to hang it and secure the rear of the power steering pump in place.

With everything topside in place and torqued to specifications, we went downstairs and hooked up our exhaust pipes to the collectors. John and Paul matched up the stock pipes to the new header collector outlets. This muffler clamp "forest" is a temporarily fix to let us drive the car over to the dyno.

Back on the dyno we saw an extra 10hp and 14 ft. lbs. of torque with the header-only installation running through the original pipe and mufflers.

Here is our starting point or should we say our curvy mess of a system as we got started at MagnaFlow's Tech Center. The Hooker Headers added horsepower but were jammed into an antiquated set of pipes and mufflers.

The first step was to clear the underside of the car of the old ratty system. Jose got out "our" favorite tool, a sawzall, and made quick work of ridding the car of past sins.

To get a better look at the complete system we put all the parts together on the floor. Note the smooth contours and even bends to aid gasses out the back quickly.

A close-up of the Tru-X crossover shows just how smooth this feature is over conventional H-type crossover systems. The extra vacuum that is created helps pull exhaust gases through the system for increased flow while controlling sound levels.

The Tru-X and intermediate pipes fit the bottom of the car like a glove.

The only modifications needed to the car for the system is to drill out the hanger holes from 5/16" to 3/8" to accommodate the new bolt-style muffler hangers.

Now we're getting to the good stuff as Jose slides the first of the mufflers into position. Like our trial fit outside the car, it is a good idea to get each component in place before tightening anything up.

Jose is about to do the only cutting and adjusting needed with the MagnaFlow Crossmember back system. Two pipes with 45-degree angles are provided to allow hook up to any header system. Designed with one length longer than the other--check fit each way, measure twice, and cut once.


MagnaFlow Performance Exhaust
Rancho Santa Margarita, CA 92688
Johns Customz & Performance
Torrance, CA

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