What does it take for a modern muscle car to sound like a classic muscle car?

Question

To preface, I would grade my exhaust knowledge with a "B-". I know what the major components are and what they do, but I don't know if and when certain exhaust parts became mandated or introduced over time.

I love how a throaty late-60's/early-70's muscle car exhaust sounds. Gnarly, a bit raspy, yet throaty and with some oomph. But when I hear most current muscle cars - 90s and on - the exhaust is mostly deep and loud, with little of the raw or explosive sound that the classic cars have. The classic muscle cars sound very similar to an inboard/outboard boat engine, where the contemporary muscle cars rarely achieve that note.

A few examples to describe what I notice... (site won't let me post more than 2 links, I posted the most representative examples of what I'm describing)

Classic sound

1970 Charger - 40 sec

Current Sound

2014 Mustang - 20 sec

• I understand straight pipes make it louder
• I understand bigger cams stagger the rhythm of the revolutions

Is there anything inherent that causes the discrepancy in exhaust note? Or do modern manufacturers and modern aftermarket performance companies prefer the "newer" sound?

Answer 1

It has very little to do with the exhaust system and much to do with the mechanics of the engine. All modern muscle cars have aluminium blocks (vs cast iron), round exhaust ports (vs rectangle), and completely different timing set ups than 60s cars have. The firing order makes a big difference because nobody fires 2 in a row on the same side of the engine anymore. Thus engines have much better balance now and are smoother sounding. It's also one of the reasons red lines are so much higher. The thin walled aluminium blocks and heads resonates sound much differently than cast iron did and even things like 6 bolt mains change engine resonance through the block giving you a tighter tinny sound. Of course just like air blowing over valves in a trumpet the shape of the combustion chambers and round exhaust ports changes the exhaust note too. In short the only way to get the 60s sound is with a 60s car.

For what it's worth I have tried nearly everything to get my LS1 Miata to sound like a real muscle car!

Answer 2

You may be able to get close to what you want by installing a stainless steel exhaust (as opposed to the standard mild steel). It will give you a more raspy sound. In addition, deleting the center resonator/muffler and adding a freeflowing sports rear box with a large tip (diameter should be larger than the diameter of the pipe coming from the cat) would help too. Just keep in mind that deleting the resonator will make the exhaust resonate in the cabin at certain RPM (usually around 2700 to 3000RPM). It may be annoying.

As folks have said, the shape, profile and materials have changed, so you'll never get to 100%, but you can come close. FYI: Porsche uses butterfly valves in the modern 911's (or at least until 2001 when I learned about it) exhaust to mimic the sound of the classic 911's like the Super 2000, 2.7RS, etc. So it's not like you're the first person to want to do this.

Answer 3

What your ears may be detecting is the camshaft specifications. In the sixties the flat tappet camshafts were the norm. To get a better picture on how a camshaft works look up "how stuff works/camshaft. Looking at the cam spec graph you will see there is a time when the exhaust valve is not fully closed and the intake valve is on its way open. This is the cams overlap, in part -LSA(lobe separation angle). The duration and overlap between different camshaft designs will give the exhaust a different sound and change the engine characteristics. Older cams needed to increase the duration and overlap to gain higher lift. Now modern car engines with fuel injection can't tolerate much overlap without throwing codes, running poorly and failing emissions. Cars of the 60s that had that great sound was due, from my experience, to the flat tappet cam which had a longer duration and greater overlap. With the advent of the roller lifter, engineers could now put steeper lobes and higher lifts into the cam but if you would tried to do that with a flat tappet cam the edge of lifter would dig into the lobe. Today's cars run with shorter duration, less overlap but very high lifts giving great performance! But without those long durations and large overlaps you lose that muscle car sound we crave.

Answer 4

I'm not a mechanic or a car expert, but like John said, that choppy, banging idle you hear from the old school muscle cars mostly has to do with the valve timing coupled with higher than average compression ratio, exhaust pipe configuration and of course, the order in which the cylinders fire matters too. These are the mainstays of the classic muscle car sound. A long duration cam with a large amount of overlap gives you that sort of popping, clangy badassness that everyone loves. If you had push-rod flat-tappet cam, maybe some longer duration and lift, you're gonna get that badass choking sound, like it's rough but mean and powerful sounding. I love that sound too. The long-duration with a lot of overlap, basically causes uneven firing or missing at low RPM that has a similar sound of a drummer playing a shuffle beat. Plus, if you add open headers or straight pipe, that's where it really starts to sound raw. Not to mention if you have a big-displacement and high compression.... ooohhhh you're cookin' now. The modern muscle cars do the ooposite... they gotta have exhausts, they are fuel-injected (which typically evens out The idle), and have less-radical cams with less overlap. Not that it's bad for performance, it's just bad for the sound that us proud, primitive car-lovers need. So bottom line is, big block, high compression, big cam and open headers=you lose your hearing. Hope that helps!