Why Upgrade Your Chevelle SS with a Borla Exhaust?

The Chevrolet Chevelle SS is an American muscle icon, and its performance potential is legendary. One of the most effective and satisfying upgrades you can make is installing a quality cat-back exhaust system. Borla has built a reputation for producing exhausts that deliver a noticeable horsepower gain, a deep, aggressive tone, and lasting quality. For the Chevelle SS, a Borla system can provide a real-world increase of 10–15 horsepower at the wheels, along with improved throttle response and a weight reduction compared to the factory exhaust. This guide provides a detailed, step-by-step walkthrough to help you complete the installation yourself, ensuring you get the most out of your new system.

Tools and Materials You’ll Need

Before you begin, gather everything you need. Having the right tools on hand saves time and prevents frustration. The following list covers the essentials, plus a few extras that make the job smoother.

  • Borla exhaust system kit designed specifically for your Chevelle SS year and model (confirm part number with Borla or a trusted retailer like Summit Racing)
  • Socket set with metric and SAE sizes (½-inch drive recommended for stubborn bolts)
  • Wrench set (combination wrenches, including 15mm and 18mm for typical exhaust bolts)
  • Torque wrench (critical for proper clamping force)
  • Jack and two jack stands (minimum 3-ton capacity for a Chevelle SS)
  • Safety glasses and heavy-duty work gloves
  • Penetrating oil (e.g., PB Blaster or WD-40 Specialist)
  • Exhaust hanger removal tool (or a large flathead screwdriver and pliers)
  • Rubber mallet (for aligning pipes without damage)
  • Anti-seize compound (for bolts and slip joints)
  • Shop rags or paper towels
  • Optional: jack stands under the frame or axle, plus a creeper for comfort

Preparation for a Smooth Installation

Park your Chevelle SS on a level, hard surface. Allow the engine and exhaust to cool completely if the vehicle has been driven—hot pipes cause severe burns. Work in a well-ventilated area, preferably a garage with the door open or outdoors. Disconnect the battery negative terminal to prevent any electrical shorts while working near sensors or starter wiring. Review the Borla instruction sheet included in your kit; while this guide covers general steps, your specific system may have unique clamp locations or hanger positions.

Dealing with Rusted Bolts and Hangers

Chevelle SS models from the late ’60s through early ’70s often have exhaust systems that have been on the car for years, leading to corroded bolts and rusted hanger rods. Spray penetrating oil generously onto every nut, bolt, and hanger stud you plan to remove. Let it soak for at least 10–15 minutes before applying any wrench. For especially stubborn fasteners, a second application and some gentle tapping with a hammer can help break the rust seal.

Step 1: Lift and Secure the Vehicle Safely

Position the jack under the rear differential housing or the frame rail, not the exhaust itself. Lift the rear of the Chevelle SS until the tires are about 8–10 inches off the ground. Place jack stands under the factory frame lift points (behind the rear wheels and ahead of the rear axle). Double-check stability by gently shaking the vehicle. For additional safety, place chocks in front of the front wheels. Never work under a car supported only by a jack.

Step 2: Remove the Old Exhaust System

Start at the back. Use a ratchet and socket to remove the bolts securing the tailpipes to the mufflers or intermediate pipes. If the exhaust has clamps, loosen them with a wrench. The rubber hangers can be stubborn; use an exhaust hanger tool or a large screwdriver to pry the metal hanger rod out of the rubber isolator. It often helps to spray silicone lubricant on the rubber to ease removal.

Work forward: remove the bolts connecting the mufflers to the intermediate pipes, then the bolts at the header collectors or manifold flanges. If your Chevelle SS has a dual-exhaust system with an H-pipe or X-pipe, support the crossover pipe while unbolting it. Rusted flange bolts may break—this is common. If a bolt shears, you may need to drill it out or use a bolt extractor, but often the remaining stud can be removed with vice grips after the pipe is out of the car.

Tip: Before fully removing the old system, note how the factory hangers attach. This will help you position the new Borla hangers correctly. Take a photo if needed.

Optional: Remove Factory Hanger Brackets

Some Borla systems reuse the original frame-mounted hanger brackets; others provide new brackets. Check your kit. If you need to remove old brackets, spray the bolts heavily and use a breaker bar. Applying heat with a propane torch can free them, but be careful near fuel lines and brake lines.

Step 3: Install the New Borla Exhaust System

Borla’s systems are engineered to fit precisely, but a little patience during assembly ensures best fitment and performance. Begin with the header collectors or manifold connections. Apply a thin bead of high-temp silicone or use the provided gaskets (if any) to create a leak-free seal. Hand-tighten the bolts, then torque to Borla’s specification (typically 25–30 ft-lbs, but check your manual).

Assemble the Intermediate Pipes

Work from front to back. Slide the intermediate pipes into the Borla mufflers or resonators, leaving the clamps loose for now. Borla systems often use slip-fit connections with band clamps. Apply anti-seize to the pipe ends to prevent seizure and ease future removal. Ensure the pipes do not contact the floor pan, frame, or driveshaft. Rotate the pipes as needed to maximize clearance.

Install the Mufflers

Position each muffler so the inlet and outlet align with the pipe runs. Borla’s mufflers are typically straight-through designs, so orientation matters—look for the airflow arrow stamped on the case. Attach the muffler to the intermediate pipe using the supplied clamp, but do not fully tighten yet. If your kit includes an X-pipe or H-pipe crossover, install it now, checking that it sits evenly between the two banks.

Tailpipes and Tips

Slide the tailpipes into the muffler outlets and route them toward the rear. Most Borla kits for the Chevelle SS exit behind the rear wheels or through the rear valance cutouts. Align the tips for a symmetrical appearance—this is the part everyone sees. Use a rubber mallet to gently tap components into final position. Once everything looks good, tighten all clamps and bolts to the specified torque. Do not overtighten stainless steel clamps; they can distort or slip.

Step 4: Install and Adjust the Hangers

Use the provided metal hanger rods and rubber isolators to support the exhaust. Push the rods into the isolators until they click into place. The exhaust should hang freely without binding or touching the undercarriage. Critical: Avoid contact with the floor pan, transmission crossmember, driveshaft, brake lines, or fuel lines. Even slight contact will cause rattles and can damage the exhaust or vehicle. If a pipe is too close to a component, loosen the clamp and rotate the pipe slightly. For tailpipes, check that they clear the rear axle and leaf springs.

Step 5: Double-Check All Connections

Go over every clamp, bolt, and hanger. Ensure all fasteners are tight. Pay special attention to the header flanges—they are a common leak point. Use a friend to help: have them push on sections of the exhaust while you listen for creaks or contact noises. If you have a torque wrench, verify that all bolted joints meet the recommended specifications. Apply a final check to the battery cable if you disconnected it.

Step 6: Lower the Vehicle Properly

Remove the jack stands one at a time. Lower the car slowly. Before fully setting the tires on the ground, peek underneath to make sure nothing is pinched or caught. Then lower completely. Turn the steering wheel lock to lock to check for any contact with the exhaust near the front wheels (if applicable). Reconnect the battery negative terminal.

Step 7: Test and Break-In the System

Start the engine. Immediately listen for abnormal sounds—exhaust leaks often produce a ticking or hissing noise. Check for smoke or fumes under the hood. Allow the engine to reach operating temperature, then inspect all joints for leaks using your hand (careful!) or a piece of cardboard held near the joints. A small leak will blow cardboard away.

Take the Chevelle SS for a short drive, varying speed and load. Borla systems often have a break-in period of about 50–100 miles during which the sound may deepen. After the drive, recheck all clamps and bolts while the system is hot—thermal expansion can loosen initially tight connections. Tighten any that have crept.

Performance and Sound Expectations

You should notice an immediate improvement in throttle response and a deeper, more aggressive exhaust note. The 10–15 horsepower gain is most noticeable in the mid-range and top end, especially when paired with a performance air intake and tune. Expect a slight decrease in backpressure, which helps the engine breathe. Some owners report a small increase in interior sound level, but Borla’s patented technology keeps drone to a minimum.

Additional Considerations for Maximum Gains

Engine Tuning

To fully realize the horsepower increase, consider a professional dynamometer tune or a reflash of the ECM using a tuner like an HP Tuners or EFI Live. The Borla exhaust reduces restriction, which can lean out the air-fuel mixture slightly if the car is carbureted. Adjust the carburetor’s idle mixture screws or jetting (if applicable) to optimize performance.

Emissions and Legalities

Check your local laws. Borla cat-back systems generally retain the catalytic converter location (if your Chevelle SS is equipped with one). However, if you are removing components that affect emissions controls, verify compliance with your state’s regulations. For classic cars, many areas have exemptions, but it’s your responsibility to ensure legality.

Weight Reduction

A Borla exhaust system is typically made from T-304 stainless steel, which is lighter than factory mild steel. Removing the old, heavy mufflers and pipes can save 20–40 pounds, contributing to better acceleration and handling.

Conclusion

Installing a Borla exhaust on your Chevelle SS is a rewarding weekend project that yields tangible performance gains and an unforgettable sound. By following this step-by-step guide, using the correct tools, and paying attention to detail, you can achieve a clean, leak-free installation that produces 10–15 horsepower and a more engaging driving experience. The combination of quality materials, precise fitment, and Borla’s engineering makes this one of the best upgrades for any Chevelle enthusiast.

For further reading and specific part recommendations, visit the official Borla website or check out the Chevelle community at Chevelles Stuff for tips and owner reviews. You can also find installation videos on YouTube to supplement this guide.