Breathing new life into the exhaust system
Story Larry Weiner
The mid-1960s through the early 1970s were an amazing time when the conversation turns to performance cars. Muscle and pony cars were all the rage, with their fresh styling and often bold graphics, especially when compared to the pedestrian-looking full-size cars.
Almost without exception, models were available with fire-breathing small- and big-block engines, backed up by four-speeds and highly-geared limited slip differentials that would easily fry even the new Wide Oval tires.
While the new cars were exciting to look at, and even more thrilling to drive, the stock exhaust systems on most of them were simply not in the same league. In fact, the exhaust systems on the performance cars of the era were often very restrictive, to say nothing of being far too quiet for the rebellious youth. To add insult to injury, they were manufactured from steel that quickly rusted out. In many cases, the result was that most of the stock exhaust systems were unceremoniously removed soon after the vehicles were purchased and replaced with larger diameter pipes and glass pack mufflers, along with headers equipped with flanged collectors that could be quickly disconnected from the head pipes for weekend forays at the strip.
When we purchased this 1967 Camaro SS350, the exhaust system consisted of old rusty head pipes, the original hanger assemblies, and what appeared to be a recently installed Flowmaster transverse muffler with tailpipes that exited in the stock location right behind the rear wheels. When the muffler was installed, it was positioned too low, so that when the Camaro was viewed from the rear, you could see it hanging down. Further aggravating the situation, the corded rubber on the original exhaust hanger assemblies was dried out, cracked and deformed from 44 years of heat transference and supporting the weight of the exhaust system. Needless to say, the Camaro was ready for a new system.
When deciding the exhaust system to use, we took several factors into consideration. We wanted a low restriction system with a slightly more aggressive sound than a factory-style replacement system with a transverse muffler, but not as loud as the Flowmasters that had been on the Camaro. Next, we wanted the system to appear visually stock from the outside of the vehicle, with the tailpipes exiting behind the rear wheels, including the use of factory-style hangers and third, the exhaust pipes would need to be configured specifically to accommodate the Gear Vendors unit located behind the Muncie M20 transmission.
Based on these parameters, it was obvious that a conventional reproduction exhaust system would not fit our needs. It led us to talk to Jim Warner, the owner of Warner’s Muffler in Oceanside, California. Jim understood exactly what we wanted and he suggested not trying to modify a stock type exhaust system. The best solution was to create a full custom system for the Camaro using 2¼-inch pipe. The head and tail pipes would closely mirror those used on a stock system, while the exhaust pipes would be specifically designed to provide the additional clearance required for the Gear Vendors Under/Overdrive unit.
For mufflers, Jim suggested using two Imco turbo mufflers, similar in size and shape to the resonators GM used on the 1967 Camaro SS396 exhaust system. Like the factory resonators, they fit neatly in the floor recesses under the rear seat area and would provide the vintage ’60s performance tone. Lastly, the system would be designed to utilize original-style muffler and tailpipe hangers. The hanger assemblies we had chosen from YearOne Inc. are similar in appearance to the original factory hangers and bolt to the Camaro with the factory attachment points and fasteners.
1 This detailed comparison photo of the original GM front hanger assembly and reproduction hanger assembly illustrates differences.
2 This photo shows the original GM tailpipe hanger assembly and the reproduction hanger assembly. You may be able to see the distortion of the corded rubber on the original hanger.
3 There are threaded bungs in the floor support for attaching the front hanger assembly. Here’s the reproduction front hanger assembly bolted into place using original fasteners.
4 There are holes in the factory subframe for mounting the tailpipe hanger assembly. The reproduction tail hanger assembly is bolted into place using original fasteners.
5 Jim Warner takes the initial visual measurement in advance of beginning to bend the head pipe for the right side.
6 Bending the head pipe on a hydraulic pipe bender.
7 The diameter of the tip of the head pipe must be compressed to match the diameter of exhaust pipe mounting flange.
8 Re-use the original exhaust flange and slip it onto the head pipe, followed by flanging the pipe.
9 Insert a short piece of pipe into the head pipe. Expand the pipe slightly to lock it into place. This creates a pipe extension to support the packing that mounts on the end.
10 Install the head pipe flange over the three studs on the exhaust manifold and tighten the three nuts to 13 to 17 lbs-ft as recommended by the Chevrolet 1967 “F” Car Assembly Manual.
11 The completed head pipe fits into the recessed area of the factory transmission mount. The end of the head pipe has been expanded to accept the exhaust pipe that will run to the turbo muffler.
12 The left side head pipe will need to be formed to provide ample clearance for the oil filter and clutch linkage.
13 The left head pipe is created to mirror the image of the right pipe, with variances to accommodate the differences dictated by the mechanicals.
14 The muffler needs to be test-fit to determine placement in relation to the front hanger assembly and the recess in the floor.
15 The electric solenoid, wiring and speedometer cable are located on the left side of the Gear Vendors unit, so clearance is critical for the pipe. Jim took measurements and the pipe is installed with the completed bend.
16 The muffler is attached to the exhaust pipe with the outlet correctly located at the front hanger assembly. Additional bends have been incorporated into the rear of the exhaust pipe to facilitate the installation of the muffler.
17 With tack welds holding the left side, work begins on the right side.
18 Both sides are now complete to the muffler.
19 All joints are welded at this time. Note the clean welds, which are critical.
20 The tailpipe hanger assembly for each side is bolted onto rear subframe in preparation for the tailpipes.
21 Jim begins with a piece of straight tubing and makes several bends to create the first tailpipe. The tailpipes require multiple bends and angles to clear the differential and fit the vehicle properly. Jim is checking his bends at an early stage in the creation of the tailpipe.
22 The right tailpipe is very close to completion.
23 After several more bends, the tailpipe fit perfectly. You can see the original GM strap clamp attaching the tailpipe to the hanger. There is not much space between the leaf spring and the quarter panel on a first-gen Camaro for the tailpipe, so a precision fit is essential.
24 Here’s the factory-like appearance of the completed dual exhaust system. Can’t wait for the road test.