Currently, there are many exhaust systems available for our Project Shark Attack's '79 Corvette, from bone stock replacements to off-road-only systems. The real trick to adding a new exhaust to a Corvette is defining what system will be correct for the application and your personal sound preferences. Keeping the sound levels to a low roar at full throttle and limiting exhaust system restrictions was our overall target. We needed to consider the complete system from the cylinder heads to the rear of the car before ordering the first piece. We wanted to know the engine was running, but long road trips with loud straight pipes just won't cut it anymore. After thirty minutes or so, most Corvettes with a loud exhaust become almost unbearable. We also wanted better airflow than the stock manifolds would provide so we began to consider header options. The header choice would also determine what exhaust system was feasible.
Another major consideration was the fact that Project Shark Attack had a catalytic converter. We wanted to install new high-performance cats to keep the air we breathe cleaner. A key factor was the heat generated by the catalytic converters. We wanted to keep them from underneath the floorpan if possible. The only other location to place catalytic converters is between the exhaust down pipe and the firewall. We now know that locating the catalytic converter close to the heat source (engine) activates them faster, and they start cleaning up the exhaust quicker. If we could place the converters closer to the engine, we could also get them out from under the floor area. The only problem with this solution is that our header choice was limited.
Upon further research, we found Hooker Super Competition's Equal length header 131/44-inch primary tubes would tune our 383's exhaust flow and add horsepower if we had the area to work it all in. The unfortunate side of this option was that the long primary tubes on these headers left no room for the cats. After further thought, we realized we really didn't need them since we wouldn't be running the engine at maximum rpm most of the time, especially with the high prices for fuel today. PSA's usage will be as a boulevard cruiser and an occasional drag strip/road course warrior. The right alternative for our job was Hooker's Street Rod-style shorty headers. These headers still feature tubes of equal length but are shorter in length. By using these pipes, we still greatly enhanced our exhaust flow and now the converters could be positioned in the engine compartment area, close to the down tubes off the headers.
First, we install the headers...
First, we install the headers using our Earl's Pressure Master Exhaust Seals. The Pressure Master seals are incased in an aluminum housing that allows you to replace the inserts without replacing the aluminum housing. The Pressure Master Seals are more expensive, but using these seals means you'll only need to replace them when it's engine overhaul time, not because of an exhaust leak.
We tack welded the mandrel-bent...
We tack welded the mandrel-bent elbows together while checking for correct fit before final welding. We used a combination of 45- and 90-degree elbows to fit the converters in place. Hooker makes a set of tubes with the 90-degree bend, but they are a little long for the Corvette application. They also decrease ground clearance. Since PSA has been lowered, we wanted the pipes as high as possible.
We left the flange loose so...
We left the flange loose so we could move the pipe around while wrapping the pipes with the Thermo-Tec heat wrap. The Thermo-Tec heat wrap was used to keep the starter, engine compartment, and our feet cool. Wrapping the pipe before the converter also helps retain heat and gets the catalytic converter active quicker. If working with fiberglass bothers you, wear gloves when applying any heat wrap.
We chose Random Technologies catalytic converters because of their free-flow capabilities and overall small size. This is one area where smaller is better. The catalytic converters have 211/42-inch in/out tubes and small converter bodies. This configuration allows more options when dealing with tight spaces.
To get the exhaust out the rear of the car, we choose Corvette Central's complete C3 system with Magnaflow mufflers. Corvette Central fabricates these systems in-house excluding the Magnaflow mufflers. If you prefer, they can also produce OE-style mufflers for the system. The Magnaflow mufflers Corvette Central provides are modified to fit using the OE hangers and connect to the OE-style pipes to eliminate custom fitting. Over the years, Corvette Central has produced many exhaust systems for '53-'96 Corvettes, so we knew when we ordered the system it would fit the confines of PSA without any extra work. We used 211/42-inch mandrel bent elbows from our local NAPA to connect the headers to the cats and then to the Corvette Central system.
Now that we had an exhaust system plan, the only thing left to consider was the hardware and gaskets to use. One of my complaints with using headers is the constant tightening of the header bolts to prevent gasket blow-out. Those concerns are a thing of the past now when the correct gaskets are used. Earl's Performance makes a graphite foil pressure master exhaust seal set that allows the bolts to be tightened and stay tightened. The pressure master sealing material seals uneven surfaces and won't blow-out. Reduced head fasteners allow the headers to be tightened properly and stay that way so we could feel comfortable about installing the headers.
Since the install was completed, we've driven the car quite a bit. Let me answer the frequently asked question: how do the mufflers sound? Well, frankly a little quieter than we expected. We expected them to be a little more raucous. The exhaust tone at higher rpm and engine load is still nicely noticeable without being obnoxious. When you're under power on the dragstrip, the exhaust sound says you mean business. We give the Magnaflow mufflers a thumbs-up, not too noisy, but noticeable when you've got your foot on the throttle.
This gives you an idea of...
This gives you an idea of what we used to install the Random Technologies catalytic converters. Yes, the elbow is too large. We used 211/42 -inch elbows that fit correctly. We mocked up the pipes then installed them loosely to check overall fit.
The Corvette Central front...
The Corvette Central front pipes were cut at approximately midpoint of the transmission, and the converters were butt-welded to the front pipes. Everything was shiny and new when we originally installed the system. Due to time constraints when we assembled PSA, we had to go back and show the assembly later. PSA was built to drive and, as you can readily see, it has been.
We also applied the Thermo-Tec...
We also applied the Thermo-Tec heat wrap at the header flange area to keep the plug wires cool. We fabricated heat shields out of .060 aluminum sheet to keep the heat off the engine block and plug wires because the header flanges are much closer to the engine block than the stock manifolds. These are the small touches that make the car drivable and reliable.
One thing we didn't like was...
One thing we didn't like was the bolt-and-nut arrangement for our flange connections. We considered welding the bolts to the flanges, but soon figured out that they were loose for a reason. With the bolts in a fixed position, it would be very difficult to remove or install the pipe once the system was completed. We also mounted the plug wire/knock sensor shield at the oil pan rail.
|ANYONE’S PROJECT | no tools required ||N |
|BEGINNER | basic tools ||NN |
|EXPERIENCED | special tools ||NNN |
|ACCOMPLISHED | special tools and outside help ||NNNN |
|PROFESSIONALS ONLY | send this work out || NNNNN |