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Discussion Starter #1
Question:
I have a 1967 fb crate 351w 400hp with headers. Are these mufflers loud? The car currently does not run and was just wondering what you guys think? I am not looking for anything crazy loud and obnoxious. And I don’t know anything about this style of muffler.

Thanks




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If that's all you have for mufflers, they they will be quite loud. Those are straight-through "glasspack" style mufflers, and pretty small at that, which makes them louder.
 

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Discussion Starter #3 (Edited)
Obnoxious loud?

This might be easier way to judge on how loud?

How loud is this going to be.
10 being crazy obnoxious loud.
1 being normal 1967 289 stock muffler stock engine stock exhaust.

Is this like a 6?

Or like a 9?

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Shorty glasspacks like yours, but bolted directly to the headers without pipes would be a 9. Maybe a 10, as they can be just as loud as open headers in the right conditions. If those are toward the back of your car, they probably do help a little, so call 'em a 7.

While very low-restriction (even more so than a straight pipe!), glasspacks are a perforated pipe wrapped in fiberglass, inside a shell. The matting gets full of soot and stops being fluffy over time (or blows out the tailpipe), at which point they tend to be pretty dang loud. Think Thrush and Cherry bombs. Usually, the longer they are, the quieter they are, but no glasspack is going to be mellow and tame sounding. They have a beautiful savage snarl, which changes to explosive cackling as you let off on the gas. Absolutely classic exhaust sound for a musclecar - but often really annoying out on the highway. The quietest glasspacks are probably going to be about a 6-7.

"Turbo mufflers" have a wider body and typically force exhaust to travel in sort of an 'S' pattern inside. They offer a lot more sound deadening, but they're also a bit more restrictive. Magnaflow is an exception to this. They are called "turbo mufflers" but they are more like 'better built' fat glasspack mufflers. They are superior in flow to most Turbo mufflers, but have better sound-deadening than a glasspack muffler. While not 'quiet', these are probably more like a 5-6 on your loudness scale, when combined with a full exhaust.

Lastly, chambered mufflers are pretty common these days. Think "Flowmasters". They come in different lengths, which quiet things down based on size more or less. Bigger = quieter. Your typical Flowmaster 44 sounds like someone lighting off packs of Black Cat firecrackers in a culvert. It is a hollow, boomy, annoying sound. Instead of depending on damping materials and perforated pipes inside, chambered muffles use baffles to help attenuate exhaust pulses. They would rate probably about a 6-8 on the loud scale. Their hoarse, sad, echoing thud attracts droves of millennials and fraternity kids with lots of money but no taste or common sense. (What? No! I'm not biased!)

The classic stock muffler setups are typically a combination of perforated pipes and fiberglass damping inside. Most of them are pretty restrictive.


Edit: OOPS. I was putting a "1" at more like "early 70s luxury car quiet". I'd say a full stock mustang with the resonators and cross flow exhaust would be maybe a 4 on that scale, so adjust my numbers accordingly!
 

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Discussion Starter #5
You obviously know a lot about mufflers. Would you keep these on or swap them out. And if I swapped them out would I have to modify anything?


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Glass packs also tend to get louder over time as the fiberglass burns out and then it is just a straight pipe.
 

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If it was my car, I would try them out for a while. If they're just too flaming loud, maybe consider using them as a resonator and adding a second muffler, or just replace them with some good turbo mufflers perhaps.


Unless you want your car to sound like Gary Busey trying to sing opera while gargling beer, avoid chambered mufflers though. Unless you like that sort of thing. ;)
 

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I recently tried the el cheapo thrush chambered mufflers on my 70. I like them. They are a 4 on loudness at idle. Nice sound on highway. Nothing like flowmaster. It sounds good to my ear, and the price was right at summit. 36 bucks each I think.
 

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Why does it not run? Maybe the best approach is to concentrate on that aspect first, start it, get it tuned and operating properly....then decide on the mufflers. However, I agree with David...probably going to be loud.
 

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Discussion Starter #10
It’s a shop doing paint body, 5 speed swap, and a hand full of other items to get her on the road.


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Mufflers

Get it on the road with what you have. If you can live with the interior sound you're halfway home. They will get louder if they are Glasspacks.
 

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I recently tried the el cheapo thrush chambered mufflers on my 70. I like them. They are a 4 on loudness at idle. Nice sound on highway. Nothing like flowmaster. It sounds good to my ear, and the price was right at summit. 36 bucks each I think.

Are those the Thrush Welded mufflers? I was actually thinking about trying them on my car. Getting kinda tired of the Dynomax Ultraflo glasspacky sound.
 

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Any 'straight through' muffler that looks like a tube is going to sound like a glasspack. Because it is, even if they don't use fiberglass matting. Just what they're called, unless it's referred to as a 'resonator' or some other thing. Awesome performance, savage exhaust note. Known for 'drone' at certain RPMs usually when out on the highway. Short glasspacks = louder, with more drone, while long ones can often be reasonably quiet. Size is everything when it comes to Glasspacks.

Another alternative which has similar performance but a slightly milder tone would be Magnaflow mufflers, because they are the same setup, but with a larger case and more sound-absorptive material. Still a straight-through muffler, but a rounded box for the housing. Less drone-y

If you want quieter still, you're going to lose some performance, going to a turbo-type muffler, which forces the exhaust to make some tight turns through an 'S' shaped path. They're much milder in tone, but still offer a nice rumble.

Chambered mufflers aren't typically quieter than glasspacks, but they are hollow sounding and annoying to my ears. Still very prone to drone, perhaps even more than glasspacks. They use no packing materials to absorb sound, instead relying on a system of baffles. They seem to attract drunken frat boys and millennials. (was that too harsh? Probably.) Okay, fine. I admit it, I'm horribly biased against them! Friends don't let friends buy Flowmasters. =) Performance-wise, they're on par with glasspacks and Magnaflows, usually.
 

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Any 'straight through' muffler that looks like a tube is going to sound like a glasspack. Because it is, even if they don't use fiberglass matting. Just what they're called, unless it's referred to as a 'resonator' or some other thing. Awesome performance, savage exhaust note. Known for 'drone' at certain RPMs usually when out on the highway. Short glasspacks = louder, with more drone, while long ones can often be reasonably quiet. Size is everything when it comes to Glasspacks.

Another alternative which has similar performance but a slightly milder tone would be Magnaflow mufflers, because they are the same setup, but with a larger case and more sound-absorptive material. Still a straight-through muffler, but a rounded box for the housing. Less drone-y

If you want quieter still, you're going to lose some performance, going to a turbo-type muffler, which forces the exhaust to make some tight turns through an 'S' shaped path. They're much milder in tone, but still offer a nice rumble.

Chambered mufflers aren't typically quieter than glasspacks, but they are hollow sounding and annoying to my ears. Still very prone to drone, perhaps even more than glasspacks. They use no packing materials to absorb sound, instead relying on a system of baffles. They seem to attract drunken frat boys and millennials. (was that too harsh? Probably.) Okay, fine. I admit it, I'm horribly biased against them! Friends don't let friends buy Flowmasters. =) Performance-wise, they're on par with glasspacks and Magnaflows, usually.
I've had these Dynomax Ultraflo on the car for approx a decade and always like them, but they just don't really sound good anymore, maybe its just me. I prefer deep rich tone. I used to think these mufflers had that. Maybe over time the sound has changed.

I originally switched to them from the Flowmaster 40 to combat the drone in 5th on the highway at around 2k rpm. I actually think Flowmaster at least the original muffler sounds great, but not a fan of the drone associated with them, which created a dislike for them. On big block pro street style Chevelles etc nothing sounds better besides open headers.

I like the sound of Dynnomax SuperTurbo, but they are too quiet for my liking.

Magnaflow sounds terrible in my opinion, esp on Mustangs. Too thin and raspy. Never heard one car that I thought they sounded good on. Actually tried one on an F150 years ago and thought it sounded like a UPS truck. I swapped that for a Flowmaster Super 40 and it sounded perfect. It of course had a catalytic convertor though.

I believe you are right though about the straight through mufflers sounding they way you describe.
 

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My other car came from the factory with chambered straight through mufflers. Since they rely on annular chambers for function, there is no fiberglass to blow out. At low and mid throttle range, they are actually quite quiet, and will in no way annoy or offend my ears or my neighbors. At full throttle, they have a very loud, pleasing tone.

 

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Question:
I have a 1967 fb crate 351w 400hp with headers. Are these mufflers loud? The car currently does not run and was just wondering what you guys think? I am not looking for anything crazy loud and obnoxious. And I don’t know anything about this style of muffler.

Thanks




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This will be fun for about a day or two and then you will likely hate it. Those are probably the loudest thing you can have besides straight pipes.
 

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My other car came from the factory with chambered straight through mufflers. Since they rely on annular chambers for function, there is no fiberglass to blow out. At low and mid throttle range, they are actually quite quiet, and will in no way annoy or offend my ears or my neighbors. At full throttle, they have a very loud, pleasing tone.




Those look like Smithy's which I've seen on a few period correct hot rods. Although they are basically big glasspacks.
 

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Those actually look like Dynomax Race Bullets. If so they’re...uh, loud... But on a high-compression engine with a big ‘ole cam not much sounds better (IMO).
 

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The take away here is most aftermarket mufflers are distinctively louder than stock and muffler sound is a personal choice. To some degree it depends on your cumulative hearing loss from sitting too close to the speakers at heavy metal concerts in your youth (lol!).

Drone at certain sustained engine speeds is often an issue, so overall gearing is a factor as well.

Whether your driving style (engine speed) keeps the engine in its drone range also depends in part on the design of your exhaust system ("H: pipe, "X" pipe, resonators, etc). For example turn downs in front of the rear axle can really be boom-y from the driver's seat no matter what mufflers you use. In my experience, the Hooker Aero-Chambers that came on my car had a sharp bark that left my ears ringing after a 1 hour freeway ride. Listen to the sound track from Bullitt to get an idea of the "before" sound I dealt with. It can be can be fatiguing over distance and adding a pair of resonators made a discernible improvement. Nice deep burble until you stand on the throttle at which point, things get real loud real quick !!

I suggest you find a local "Cars and Coffee" event and take the time to listen to what rumbles into the parking lot. Talk to the drivers to see what they are using. Consider that the mufflers are one part of a system and the other components should be chosen carefully as well.
 
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