Technically Speaking: Exhaust System

James Berry Mar 13, 2013 0 Comment(s)
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Q: I’m interested in replacing my C5’s stock exhaust system, and I’m hoping you can help me determine which one is right for me. I’m looking for an aggressive sound and improved performance.

I also have a question on header selection. Specifically, should I purchase the long- or short-tube variety?

I don’t have a repair shop in my area that I trust to do the insulation, but I’m a good shade-tree mechanic. Do you think I could perform this installation in my home garage? If so, could you give me some tips to make the job easier?

Johnny

Via email


A: The C5’s factory exhaust system sounds decent and is extremely efficient. However, due in part to government decibel restrictions, the muffler design is not as free flowing as we’d like. As a result, there’s horsepower to be gained by installing a less restrictive system.

The first thing to keep in mind when purchasing an exhaust system is the quality of construction. If you go with a company that has a proven product, you usually will not be disappointed.

My suggestion is to go to several Corvette events and see which system sounds the best to you. Then, ask the car’s owner the following questions:

- Who manufactured it?
- Did he install the system himself, or have it done by a professional?
- Have there been any problems since the installation, such as rattles or a check-engine light?
- Did the kit come complete? If not, what else was needed?
- Did the system seem to boost performance, whether subjectively or on a dyno?
- If the owner had it to do over again, would he buy the same system?

Headers
To get maximum performance out of a new exhaust system, a set of headers is essential. While it’s not mandatory, I recommend buying your headers and other exhaust components from the same manufacturer whenever possible. This usually ensures that everything fits properly and lines up correctly the first time.

Vemp 1303 01 Z Technically Speaking Exhaust System Exhaust 2/7

Fortunately, installing headers isn’t especially difficult on the C5; you’ll just need a little time and patience. Make sure the ones you buy don’t require any cutting, welding, fabrication, or other post-purchase modifications.

As you noted, you will need to choose either long- or short-tube headers for your C5. Long-tube headers improve scavenging and take advantage of exhaust pulses to emphasize power and torque throughout the rpm range. The downside is that, because they require the removal or relocation of the factory catalytic converters, they are not legal for use on street-driven vehicles.

Short-tube headers are compatible with the stock cats (and easier to install), but they tend to make less power. Consider the pros and cons of each type of header carefully before making your decision.

Part 1: Removing the Stock Exhaust Manifolds
While it is possible to install your headers and exhaust system using jackstands, the job is considerably easier if you have access to a lift. You’ll also need an assistant to provide an extra set of hands during the installation.

We’ll begin by clearing out some components to make sure we have a clear path to the factory exhaust manifolds.

1. Remove the battery shroud and battery.
2. Remove the two plastic coil covers.
3. Remove the serpentine belt and alternator.
4. Remove all of the spark plugs.
5. Unbolt and move the coil packs out of the way, taking care not mix the firing order. You can label the wires and coil packs to make this easier.
6. Loosen the primary O2 sensor from the collector of each exhaust manifold.
7. Unbolt the air-injection line from the top of each exhaust manifold.
8. Unbolt the bottom (collector) of the exhaust manifold at the three-bolt exhaust flange, where the manifold connects to the exhaust pipe. This needs to be done from the underside of the vehicle.
9. Unbolt the top of the exhaust manifold from the cylinder head and carefully remove the manifold through the top of the engine compartment.

Part 2: Bolting on the Headers
1. Begin with the driver-side header.
2. Apply anti-seize to all threaded components, such as O2 sensors, spark plugs, bolts, etc.
3. Loosen the motor mounts to raise the engine for easier access.
4. You’ll need to remove the intermediate shaft from the steering box so the driver-side header can be installed. Take care not to damage the plastic power-steering-pump pulley during this process.
5. You may need an extra set of hands to help move the engine so you can maneuver the header into place. Be careful not to damage any components during this process.
6.Install the header-to-cylinder-head gasket. (Note that some kits do not come with the necessary gaskets. If yours did not, you’ll need to purchase header, collector, and air-injection-tube gaskets separately.)
7. Bolt the top of the header to the cylinder head using the factory-recommended torque rating. Tighten from the center of the flange out.
8. Install the O2 sensor.
9. Install the air-injection line in the same manner and location it was originally.
10. Install the spark plugs, taking care to route the plug wires so they’re not damaged by heat from the headers.
11. Moving to the passenger side, you may need to extend and reroute several wires for the starter to clear the headers (Image A). Locate the T-shaped junction in the wiring harness at the rear of the passenger-side cylinder head. Remove enough of the protective tape at the joint to allow the removal of about an inch of the plastic loom that runs down to the starter. Disconnect the wires and removed the starter. Then, extend each of the wires going to the starter by approximately 14 inches and position them through the rear header-tube loop to prevent them from being burnt.
12I recommend installing a length of heat-shield tubing over the starter wires, the positive battery cable, and the engine oil-sensor lead (Image B).
13. Some header applications require extending the crankshaft-position-sensor lead. If this is needed in your case, make sure the necessary part is included in your kit. If not, you’ll need to buy it separately.
14. Fasten all coil packs and spark-plug wires, making sure the firing order is correct.
15. Install the alternator per the factory recommendations.
16. Double-check everything, then replace the plastic coil covers.
17. If you’re only installing short-tube headers, and no additional exhaust parts, connect the headers to the collectors, reconnect the battery, and you’re done. Otherwise, you’re ready to move on to the next step.

Part 3: Installing the Rest of the System
1. Unpack the entire system and lay the components out on the floor. Then, check the instructions to make sure all the required parts are present. This will also give you the opportunity to orient all the components prior to installation.
2. Before removing the factory exhaust system, note the placement and positioning of the clamps, bolts, and hangers.
3. Remove the oxygen-sensor leads and clips.
4. Remove the exhaust pipes and tips, then drop the mufflers. You may find that first loosening and moving the rear stabilizer bar makes this step easier.
5. Remove the remainder of the factory exhaust components.
6. Install the new H- or X-downpipe and catalytic converters (Image C).
7. With the rear stabilizer bar still loosened or removed, route the new tailpipes over the rear-axle assembly (Image D).
8. It’s a good idea to trial fit and align the mufflers and exhaust tips before bolting everything into place (Image E).

A Corvette owner with average mechanical skill should be able to complete this job. Keep in mind, however, that it may take a few days, especially if you’re not using a lift. If you get in a bind, you can always call the manufacturer’s support line. Good luck. vette


Questions?
Got a question for our Tech Corner expert? Just jot it down on a paper towel or a lightly soiled shop rag and send it to us at VETTE Magazine, Attn: Technically Speaking, 9036 Brittany Way, Tampa, FL 33619. Alternatively, you can submit your question via the Web, by emailing it to us at vette@sorc.com. Be sure to put “Technically Speaking” in the subject line.

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