As any muscle car enthusiast will attest, sound is a big part of the overall experience. Whether it’s the rumbling idle, the authoritative bark as you dip into the powerband, or the thundering roar at wide-open throttle, a muscle car’s sonic signature is a core component of its charm.
But the exhaust isn’t up to snuff, it can add a sour note to the proceedings that really dampens the excitement. And as Holley Performance Sr. Product Manager Mark Emerson points out, simply ignoring these problems can create bigger – and potentially more costly – issues over time.
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“That’s especially true if it’s a situation where an exhaust system component is hitting something else because an exhaust hanger has broken, or a rubber isolator has rotted away. If the exhaust shifts down or falls, it could hit the rear axle, fall underneath the vehicle and take out a brake line, or create other problems.”
Emerson notes that although muscle cars aren’t inherently more susceptible to exhaust system issues than any other type of vehicle platform, the tendency for owners to mix and match aftermarket components can create more opportunities for problems to pop up. This is particularly true for pro touring builds, which often integrate chassis components that the original platform designers never could have anticipated.
“When we develop an exhaust kit for, say, a Chevelle, it’s essentially designed to work with an otherwise stock setup. And that covers the vast majority of the folks out there. But with so many different ways to customize these vehicles, particularly when it comes to suspension – coilovers, four-link swap kits, and that kind of thing – it can create challenges. Sometimes it’ll require a builder to fab up something custom, which is why we offer universal exhaust pipe kits that they can use to craft something like that. And that’s also why the exhaust is often the last piece of the puzzle in those types of builds.”
Although the cause of exhaust system noises can be tough to pinpoint from the driver’s seat, some of the most prevalent issues have tell-tale characteristics that can make the troubleshooting process less of a trial-and-error affair. Here we’ll take a look at the most common offenders when it comes to exhaust system noises and how to address them.
(While this type of work should ideally be done when engine and exhaust components are cool to the touch, wearing heat-resistant gloves is strongly recommended if the vehicle has been driven recently. And since you’re probably going to be working under the car, eye protection is also a good idea.)
If you hear a ticking sound or a hiss that seems to match the rhythm of the engine’s idle, there’s likely a leak somewhere in the exhaust system. Exhaust leaks not only give off a jalopy vibe, they can also impact engine performance and throttle response, and in modern muscle cars, they can also prevent a vehicle from passing a smog check. While these leaks can be tough to hunt down, Emerson offers some suggestions that can make process a lot easier.
“Start at the engine and work your way back. Exhaust leaks that are caused by a failed header/exhaust manifold gasket at the cylinder head will create a ticking sound, and you’ll get that same sort of ticking sound if it’s a bad gasket at the collector. Things just wear out; header bolts can start to corrode over time, and that can cause leaks as well. You’ll typically see some black soot around the area where the exhaust gases are leaking out. And after the engine has been running for a few minutes, you can typically see some condensation coming out of that area as well.”
While these noises are occasionally caused by a cracked exhaust manifold or a hole somewhere along the exhaust system, more often that not they’re an indicator that a gasket has failed or the exhaust system is misaligned somewhere along the route to the tailpipes.
“If it’s something as simple as a bad gasket, that’s just a matter of swapping out the old gasket for a new one,” says Emerson. “If it’s a flat gasket surface, it’s important to make sure that the two flange sides are lining up properly. It might be a situation where you need to adjust the angle of one of the flanges so that they bolt together properly and create an even seal. A lot of folks also like to use soft copper gaskets rather than paper ones in these types of scenarios, as they tend to be a bit more forgiving.”
A metallic rattle or thumping sound coming from the undercarriage is typically an indicator that the exhaust system is making contact with something that it isn’t supposed to make contact with. While the culprit is often obvious just by getting under the vehicle and looking for areas where the exhaust system looks to be a bit too close to another component, other situations may require recreating the sound by wiggling the exhaust around or tapping it in different areas with a rubber mallet.
“A lot of times we find this sort of issue where the exhaust system goes up and over the rear axle,” Emerson says. “You’re trying to clear the axle but you also have to allow for suspension travel – you go up and over, but you don’t want to get too close to the floorboards, and you’re trying to snake around shocks, crossmembers, and other components.”
Although the problem area is often easy to identify, sometimes hunting these noises down requires more extensive investigation due to the way that metal expands as it heats up. If the rattling or thumping noise only happens occasionally or under specific circumstances, it’s a strong indicator that exhaust system clearances aren’t adequate for the range of situations that it operates in.
“If you’ve got a really tight clearance of, say, an eighth of an inch in an area when the exhaust system is cold, there’s a good chance that pipe is going to make contact with that other component once exhaust pipe heats up,” he says.
“I actually ran into a situation like this with my truck not too long ago: The truck has large aftermarket skid plates on it, and the area where the factory mid-pipe crossed under the transfer case was always very close. Recently I was testing a different exhaust system on the truck, and the mid-pipe’s position got tweaked a bit during that process, which reduced that clearance even more. Under normal driving circumstances it wasn’t an issue, but every time I put the truck in reverse, the change in torque kind of rotated things in a slightly different way, and that was enough to cause the mid-pipe to make contact with one of the skid plates and make a squeaking sound while the vehicle in reverse because the two parts were rubbing against one another.”
Emerson tells us that correcting this is typically just a matter of loosening exhaust clamps or brackets and doing some adjustments, but he also cautions that a deteriorated rubber isolator or a broken exhaust hanger can cause these types of problems as well. While the former can just be replaced with a new isolator, the latter will likely require welding to repair.
On newer vehicles, a rattling sound can also indicate that the heat shield on a catalytic converter has come loose, which will also likely require welding to repair. This is another situation where tapping different areas of the exhaust system can help pinpoint where the problem is.
If you’ve noticed that the volume of your exhaust system has started to increase and the tone seems a little off (or is accompanied by unusual pops and bangs), it’s a good indication that a muffler is starting to fail.
“Mufflers can deteriorate over time, and if a hole develops in it, it can cause noises like that,” says Emerson. “Leaks in other areas of an exhaust system can also cause it to get louder. Welding a patch onto that section might provide a temporary fix in a pinch. But if a piece is rusted out in one spot of an exhaust system, the rest of that part is probably not far behind, so replacing that section is the best way to address it in most situations.”
He adds that while noises like these can be a source of frustration, modern exhaust technologies can help reduce the likelihood of these types of problems developing in your ride.
“There’s so many different options out there now – whether it’s a custom system created with one of our universal pipe kits or one of the many application-specific exhaust kits that now exist for both vintage and modern muscle cars, there’s a lot of different routes you can take to get an exhaust system that sounds the way you want it to. And with things like V-band clamps and copper gaskets now commonplace, it’s much easier to put together a bulletproof system than it was back in the day.”
