Jim Smart
December 1, 1999

Step By Step

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We’re installing the Mustangs Unlimited/ Flowmaster dual exhaust system on a 1970 Mustang Sports- Roof with a 302 V-8. When we put this Mustang up on a lift, we were stunned at its factory original single exhaust system. A dry California climate made that possible.
The original exhaust system was cut off at key points--the Y-pipe, hangers, and exhaust manifolds. WD-40 helps at the exhaust manifolds. If you encounter a stubborn nut and stud, heat the nut cherry-red with a torch, then remove the nut. Heating makes the nut expand for easy removal.
With the old exhaust system out of the way, we’re ready to look at the Mustangs Unlimited/Flowmaster system. Mustangs Unlimited provided us with the H-pipe (which is adjustable for headers), exhaust pipes, tailpipes, and a duo of Flowmaster three-chamber mufflers. This exhaust system can be tweaked for specific applications. Magic Muffler recommends welding all of the joints for a leak-tight system.
Because the Mustangs Unlimited/Flowmaster dual exhaust system is designed for header use, we had to fabricate two exhaust pipes for the manifold to H-pipe. This happened because we originally ordered this exhaust system for header use. You can specify with or without headers when you order your Flowmaster system from Mustangs Unlimited. Magic Muffler took the dimensions and fabricated two pipes to correct our ordering mistake.
Magic Muffler was able to fabricate exhaust flanges just like the factory for vintage Fords. First, the tube was flared, then a fire block (tube) was rammed into the pipe to protect the doughnut gasket. Does your local muffler shop show this kind of attention to detail?
The exhaust pipes are installed loosely first for adjustment purposes.
The H-pipe was test fitted and checked for clearance.
Then it was welded permanently for a leak-tight seal.
Exhaust pipes between the H-pipe and mufflers were fitted next. Any tweaking on the tubing bender comes next, then fit check, then welding.
Because not all exhaust systems are dimensionally perfect, sometimes Magic Muffler has to trim, tweak, and flare the tips for a better fit. This piece of equipment expands the tube as necessary. Magic Muffler can also shrink the tube.
The Flowmaster muffler is fit-checked first, then trimmed as necessary for proper fit.
You can cut some of the pipe off either end for improved fit, or expand each end for a better fit. Then it’s a matter of jockeying the muffler into place and checking all clearances prior to welding.
Tailpipe installation is a challenge on vintage Mustangs. Magic Muffler works hard to achieve a perfect fit, then the tailpipe is welded to the Flowmaster muffler. This is tough to duplicate in the home driveway or garage.
The Flowmaster muffler is welded to the tailpipe as shown. This means no exhaust leaks or failure.
Because we didn’t want to drill unnecessary holes in the floorpan, Magic Muffler employed the rear seatbelt bolts as attachment points for the muffler hangers. A bracket was welded to the Flowmaster muffler as shown, then a rubber hanger was tied to the bracket. If you’re not fond of this idea, then you will need to drill a 5/16-inch hole in each side above the muffler/tailpipe joint and attach the hanger there.
The left side follows the right side. Fit check, then trim as necessary, then weld. Always ascertain clearances and fit before welding.
Tailpipe tweaking was necessary on the left side of our 󈨊 Mustang as well. Fit is checked and the pipe is worked on the tubing bender until a perfect fit is achieved.
Like the right side, the left side tailpipe is welded to the muffler as shown.
Once complete, the left side should look like this. Same drill, with the use of the seat belt bolt as an attachment point.
Because our Mustang doesn’t have a GT or Mach 1 valance, we’re going to do it like a Boss 302 or 429--with hidden tailpipe tips. Magic Muffler fabricated these tips in a matter of minutes.
The clamps are turned up to keep the threaded ends out of sight. This should always be a consideration. Keep all muffler and pipe clamps out of sight.
Tailpipes are supported via the tie-down bracket bolt holes as shown. Then install the rubber hanger and clamp. Once installed, it’s stealthy, just like the Boss Mustangs.
You won’t believe the throaty sound of three-chamber Flowmaster mufflers through a stock Mustang dual exhaust system. Fit is outstanding, thanks to the help of Magic Muffler.

What gets your attention most with hot restomods? Is it the slippery, classic lines clad in fresh urethane paint? It's hard not to like those saucy aftermarket wheels wrapped in obese BFG Comp T/As. Can't knock those aggressive bucket seats bent on comfort either. But it was the throaty dual exhaust note that drew your attention first, now wasn't it?

The music makes the ride, both inside and out. Over the past 15 years, exhaust tuning has become something of a science. We used to weld steel around a bunch of baffles and called it a muffler. Originally conceived to arrest exhaust-induced sparks that might start a fire, mufflers were also born of the need for quieter motoring.

For performance applications, Flowmaster was the first to pioneer real honest-to-goodness exhaust tuning back in the 1980s, combining both performance and sound. If you’ve ever listened to the throaty roar of a 289 High Performance Mustang GT or a well-tuned Boss 302 or 351, then you understand the sweet sound of Ford performance. It’s a rich, throaty sound that gives your emotions and goose bumps a rise to the surface.

Rich sound comes from the use of Flowmaster mufflers, so we called Chris Hoverman at Mustangs Unlimited to ask him what was available for classic Mustangs to improve not only performance, but the exhaust note. He suggested a revised stock dual exhaust system for vintage Mustangs that will accommodate Flowmaster mufflers. We then contacted Mustangs Etc. in the San Fernando Valley, looking for a test mule on which to install the system from Mustangs Unlimited and Flowmaster. Arnold Marks of Mustangs Etc. ponied up with a 1970 Mustang SportsRoof project, then we headed over to Magic Muffler a couple of blocks away.

Mustangs Unlimited provides the basics for a terrific exhaust system upgrade, which includes the H-pipe, exhaust pipes, two Flowmaster three-chamber mufflers with 2-inch inlet/outlet, two tailpipes, and installation hardware. Because some minor modifications may be required with this exhaust system, we suggest visiting a trusted muffler shop for installation.