by Chirag Asaravala

How good do you think your Mustang's exhaust system sounds? We bet many of you aren't entirely happy with it. Maybe it doesn't have the muscle-car rumble you expected, or perhaps your selection of 3" pipes and straight-through mufflers have your spouse and neighbors hating you.

Whatever the case may be, we are all too aware of how tough it is to put together a decent sounding exhaust system for early Mustangs. Surprisingly, there aren't very many complete systems designed for these cars. As a result, guys must resort to cobbling together an exhaust from an endless number of combinations of headers, crossover pipes, and mufflers. And there is no telling how it will sound until it has been purchased and installed.

I'm guilty as charged when it comes to our Project '67 Mustang. A number of years ago I wanted to put together an exhaust system that wouldn't hold back the 331 stroker we'd just built. In my over exuberance for minimizing restriction, I selected 3" tubing and the virtually straight-through "Terminator" mufflers. To compound the problem I went with turndowns. The end result was a system that performed well at the track, but otherwise was so obnoxiously loud that I hated driving the car for extended periods of time.

I lived with this raucous system for years, and dreaded the thought of rolling the dice again with a new combination. But earlier this year our buddies over at Flowmaster told us they were about to release a 67-70 Mustang exhaust system. They had spent considerable time in developing the system, bringing in a number of test cars to ensure the right balance of muscle-car sound and power. Of course they also ensured proper fitment, mounting points, and ease of installation. Needless to say when they told us that they were ready to roll this kit out to the public, we quickly volunteered Project '67 as a media guinea pig. I drove the car up to Flowmaster headquarters in Santa Rosa and spent the day with the guys in the R&D shop watching and learning how pros install exhaust systems. Check it out.

We're installing Flowmaster's new American-Thunder exhaust system for 1967-1970 Mustangs. The kit is 2.5" mandrel-bent tubing and features the aggressive sounding Super 44 mufflers. Shown is part number 17282, which has turndowns at the rear valence. For Mustangs with the GT style exhaust tip cutouts in the valence part number 17281 offers Flowmaster's chrome 3"tips.

We felt privileged to have our Project '67 up on the R&D rack at Flowmaster headquarters in Santa Rosa, CA.		The Flowmaster R&D facility is used to design and test install all kinds of exhaust applications. Needless to say the shop is equipped with anything and everything needed to get the job done. More importantly it is staffed by very knowledgeable and talented Flowmaster employees.
The Flowmaster crew checks out Project 67's existing exhaust system - a 3" crossover through Flowtech Terminator mufflers. This system worked well at the track but sounded like "rocks in a trashcan" on the street, as one neighbor put it bluntly.		The old system initially dumped right behind the mufflers, but a couple years back we had tailpipes made up in attempts to cut down on the interior racket. Of course the compression bent 2.5" tubing negated the benefits of the 3" pipes up stream.
A comparison of our cobbled together 2.5" tailpipes (left) and the mandrel-bent Flowmaster tail pipes which come in the 67-70 Americna Thunder exhaust kit.		Enough analysis of the old pipes, Terry promptly removes the old system.
With the old 3" system on the ground we get a better look at how it has been cobbled together over the years as a result of header changes and other interfering components. The 3" tubing was compression bent in several spots - effectively making it flow like 2.5" tubing.		With the old pipes out of the way the underside of Project '67 is a fresh canvas for what will finally be a sane and properly designed exhaust system.
Rather than weld up a random exhaust hanger under the car, Flowmaster includes these custom support hangers which will mount to the rear seat pans.		The instructions call for specific positioning of each hanger on the underside of the seat pans. Measurements are taken from the frame rail and down from the seam in the sest pan. Terry the ncenter punches drill points for each hanger.

(Installation continued)