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 |
The Random Technologies catalytic...
The Random Technologies catalytic converter fits nicely in the area, but it's close to the firewall and footwell. We used some .100 steel to fabricate heat shields and welded them directly to the cat. The heat shields really work-no hot feet and you can see that we've driven the car in most every condition possible from the corrosion. After many miles, it's obvious the converter placement was the right choice. Overall, the floor is much cooler, and the passenger compartment is comfortable.
The rear pipe slips onto the...
The rear pipe slips onto the front pipe and gets clamped with the clamps that are supplied in the Corvette Central exhaust system. The rear pipes fit correctly with no modifications. The only modifications were at the front for the headers. Since we have the Keisler Tremec five-speed in place, we fabricated a custom bracket to retain the exhaust at the transmission. Corvette Central supplies a new transmission exhaust mounting bracket when the system is changed from single to duals when you have an OE manual or automatic transmission.
Once the front pipes are in...
Once the front pipes are in place, we install the mufflers. A light coating of never-seize allows the pipes to slip on easier. Plus, the never-seize allows you to move things around until the system is properly aligned. As you can see, the Corvette Central supplied Magnaflow mufflers have the correct pipe welded in place and is ready for installation.
when we install the clamps,...
when we install the clamps, we put the saddle "up" to keep the threaded portion from hanging down to be caught on the ground. Whether you put the clamp up or down, always watch the placement to avoid spring contact. The TRW composite spring is wider than the original metal spring and can be damaged by the exhaust clamp.
Before we fully tightened...
Before we fully tightened the rear clamp, we found that the rear pipes would hit our Vette Brakes and Products Smart Strut rear camber bracket when they were in the correct position. Our handy air hacksaw took out just enough material to allow the pipes to fit properly. Always be conservative when you cut or modify parts for a better fit. If you remove too much material, the part can be weakened. OE camber struts wouldn't require any cutting because they position the camber struts up higher, which, unfortunately, effects suspension geometry in a negative way.
It's hard to see in the photo, but the exhaust tips are black chrome, which went well with the PSA color scheme. They weren't high dollar, but were heavy gauge steel and should last a while. The tips were too long so we cut them off and welded them in place avoiding the screws that were supplied for retention.
As you can see the Corvette Central system fit perfectly from front to the back. Although our '79 shark didn't come with duals, you would never know it from the fit of the system. The aluminized exhaust pipes will last for quite a while with the electronic fuel injection. As an added benefit, this system won't be expanding and contracting like a stainless system would.
We like the fit of the Magnaflow muffler under the bumper. The mufflers fit in place correctly and required no massaging to get in the correct position. There's a fine line when it comes to positioning the muffler at the correct height. If installed too low at the rear, the pipes will be too low. If you install the muffler too high at the rear, the pipes will hit the rear camber strut bracket.