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Topic Review (Newest First)
12-16-2004 05:45 PM
THADD Man I just spent 15 minutes on a reply and the system lost it !!!!
Here I go again.
There are a bunch of things that affect sound. On a V-8, firing order changes the way an engine sounds. You can actually hear the difference between a Ford 5.0 and a 350 Chevy.
Camshaft design can affect sound. A longer exhaust duration and a tighter lobe separation make for a louder engine.
Compression ratio affects the sound. Higher compression, equals louder.
Engine size affects sound. If you have two cars with the same everything except size, the larger one will be louder (think Pontiac, Buick, Olds) The smaller engine will also sound crisper. Think big block vs. small block.
Exhaust pipe size changes the sound. Larger pipes make more noise. A 3" system is WAAAYY louder that a 2" system.
Muffler design makes a difference. In talking about mufflers, a larger muffler makes more power and is quieter than a smaller muffler.
A two chambered Flowmaster is louder than a three chamber (50 Series), but the 50 makes more power. A 70 series big bodied three chamber makes more power that the 50 series, but is quieter.
I particularly like Dynomax mufflers. They are a combination of a chambered muffler that also has packing. Their welded mufflers include Race Magnums that I think are pretty loud. Their bread and butter muffler is the Super Turbo. The Super Turbo have a 17" long body and are fairly loud, but they don't have the interior drumming that a Flowmaster has. I run Hemi Super Turbos, which are a big Body Super Turbo. These are 23" long and are quiter and make more power that a Super Turbo. They also make the Ultra Flow mufflers. An Ultra Flow is a Super Turbo with a stainless case.
Many manufacturers make packed chambered mufflers, and Edelbrock even sells a kit to repack their mufflers (what a concept).
Turbo mufflers are usually inexpensive generic stock chambered mufflers that have some sound(but not much tone) because they are short, and have some power because there is not a whole lot of chamber size.

Glasspacks (and steelpack such as Smitty's) come in lengths from 6" to over 48". The longer it gets, the more mellow it gets. Anything over 30" or so has that classic "motor boat" sound. Because it is a straight through muffler, it makes decent power but in shorter lengths it will be loud.
System configuration makes a difference.If the system has an H pipe or an X pipe, it will be mellower and make more power. The H pipe increases low end power and smooths out the exhaust pulses to take the raspyness out. An X pipe seems to do it better, because it actually forces the flow from each side to mingle.
In some cases, headers will be a little louder than cast iron manifolds primarily because the cast iron soaks up some of the sound..But there is not a significant difference. The quality of the sound is different because headers make a unique underhodd noise that, to me, is not unpleasant.
Vehicles that have full tailpipes sound crisper and less resonant (droney) than those that have turn downs under the car.
I lost a bother in law to carbon monoxide poisoning, so I am very careful with preventing CO to enter the passenger compartment. If there is a compelling reason to not run tailpipes out of the back, I will at least kick them outside of the body line ahead of the rear wheels. I prefer to have them come out the back, but kicking them over the axle and then out the side behind the rear tire is a good option.
Tips affect sound, but not significantly. A flat tip will make the sound raspier, a turn down will lower the sound, a round or oval tip bigger than the tail pipe will magnify the sound a bit (That is why they call them Echo Cans).
If you want to really throw a monkey wrench into all this, compare the sound of a V8 with that of a straight 8 with duals (one of the sweetest sounds ever), or compare a v8 with a straight 6 with duals. Then toss in a v6 with duals and it gets even crazier....The differences are all related to crankshaft phasing, firing order, etc etc.
Then we get into sound quality. What is loud to me might not be loud to you. What I think has a good tone will sound ratty to someone else.
At my shop, we sold 40 series Flows if the customer wanted it loud, and Super Turbos if he wanted it quiet..But sometimes it didn't work out that way. I vividly remember a Ranchero with a 351C that we put Super Turbos on, and it was so loud, the guy got stopped on the way home from my shop for noise. We finally got it quieted down by adding an H pipe and a pair of 9" glasspacks in each tailpipe...I had trouble getting my 383 powered S-10 to quiet down. I put Flows on it and couldn't stand them. I put super turbos on it and it sounded like it had some really short glass packs on it. I finally put DynoMax Z plus mufflers (like a Hemi) and finally got it quiet...We can't have a 12 second sleeper that is noisy can we????
The answer to you question about a stock 350 with glasspacks is that, if they are long enough, it will sound great...I would go with 32" and an H pipe...It will sound really good.
12-16-2004 01:18 PM
Nightfire Ok, out of all the replies I conclude that intake manifold, firing order, camshaft, header size, exhaust tube size, muffler type and location determine engine sound.

Thanks guys

12-15-2004 01:11 PM
killerformula It seems as though there are probably a million things that effect the sound of an engine. I think most of it probably has to do with the type and size of exhaust, etc. There is the unmistakable fact, though, that a 4.3 liter v6 (which is a 350 with 2 fewer slugs) sounds nothing like a 350. Why? Even if you disconnected two wires on the 350 it wouldn't sound like the 4.3. I can't explain that. Probably something about the amount of expansion room the exhaust gasses have, the total volume of gas in the exhaust etc.

Cams are easier to explain. A car idles choppy because the overlap of the cam is allowing dirty exhaust to remain in the chamber, because the air velocity is not yet high enough to create the scavenging effects needed to move fuel/air into the chamber and suck the exhaust gasses out. Essentially, its running choppy because its re-burning dirty air.

Mufflers just redirect and cancel some if not most of the sound waves traveling down the exhaust. Packed mufflers cancel more sound than welded, in most cases. I prefer welded, some don't like the tinny timbre to them, but they last longer than packed and rap on their way down well.

12-15-2004 09:45 AM
DesmoDog Kinda hard to explain it all in a little post like this... keep in mind there are people who make their living dealing with how the exhaust sounds. I've done a few myself... Ford T-bird, 2001 Harley Edition F150, and others.

Everything mentioned will make a difference. Anything that changes the power of the engine will also change the sound. Simply changing the timing can change the sound.

Manifolds play a big part in the sound. If you analyze the sound, the results are typically tied to engine orders. A V8 fires four times per rev, so (assuming it's an even firing engine) fourth order is often dominant. But, if you have unequal length downpipes, or uneven firing intervals (i.e. Harley Davidson) you will create "odd" orders, which some people think sound powerful. Typically "even" orders sound smoother than "odd" orders...

In general, small pipes filter out low frequencies more than larger pipes do. Long pipe lengths can add drones to the exhaust note, this typically gets worse as the pipe diameter goes up. One thing to keep in mind - mufflers don't do anything other than filter sound. If the engine isn't making the sound to begin with, a muffler can't add it in.

And of course there are exceptions to about everything I've mentioned, but like I said, people make careers out of this so you can't get it all in one post... Plus, sound is subjective. Different people perceive things differently so what sounds nice to me may sound weak to you.

Oh yeah, last comment. For the record, I think loud pipes suck.
12-15-2004 09:31 AM

I think the duration of the cam plays the biggest role in getting a good sound. But if you have a cam that has a lot of duration and stock mufflers its not going to sound great. just my 2cents worth
12-15-2004 09:21 AM

My street rod has a mild cam in a 350SBC, I originally had Turbo's which gave a deep sound but no snap, pop or cracks like glass or steel packs. I had it changed to add a H Pipe between each side and added Flowmasters. It gave a deep sound but much richer. Cool thing is that at about 25 miles per hour it hits resonance and rattles my neighbor's windows as I leave the neighborhood. Just got to love it>>>>DAVE
12-15-2004 06:10 AM
redsdad Firing order plays a part. This affects the timing of the individual pulses in the given exhuast (assuming dual outlets). The same principal applies to 180 deg. headers where you have one tube crossing over from each side. A very unique sound.
12-14-2004 04:52 PM
Mr Ed

With the muflers removed; the cam plays the biggest part as far as the overall engine sound, a standard cam will allow the engine to idle very smoothly and give a restrained nice acceleration sound whereas a big cam (lumpy) will have a rougher idle and a 'full on' sound under acceleration. Fuel Injection runs smoother than carbs and affects the sound also. Turbo mufflers are generally louder than glass packs but it depends how restricted the glass packs are as they vary from different manufacturer. Header primary length/size and expansion chamber or collector length also affects the sound as does valve size, head chamber size and piston design type. Most engines with headers and open pipes will sound quite crisp and flat until under load within the cam range. deep sounds are generally due to freeflow mufflers and tailpipes. If you have your tailpipes short on mufflers that finish ahead of the rear axle then you get a very deep droning sound which shakes the neighbours windows (this may be illegal as the potential for carbon monoxide to enter the vehicle is high). Larger diameter pipe generally makes more noise too. Standard engine with headers and glass packs will be as loud as the glass packs are restricted and the tail pipe length.
12-14-2004 04:48 PM
pro70z28 My philosophy is ......... if you build it with enough horsepower, the "Good Sound" will take care of itself
12-14-2004 04:36 PM
Siggy_Freud Cam will change the sound and idle quality. Generally, the bigger the cam the more lumpy it idles and sounds. Firing order has some to do with the sound as well as the actualy Cubic Inches of the engine. Headers, heads, etc. will also vary the sound of the engine somewhat.

Mufflers probably determind sound the most. Glasspacks are louder than turbos. The stock sbc with headers and glasspacks would sound loud. Kind of hard to describe the sound though. I personally dont think they sound that great but its all relative I suppose.
12-14-2004 04:25 PM
What determines engine sound?

Might sound stupid, but what determines the engine sound? Obviously number of cylinders. But lets assume they're all V8's. What exactly gives you the deep sound? Or the choppy rough sound?
I've hear that the cam plays a big role in the sound. Also headers and exhaust off course.
Now are glasspacks louder or turbo-mufflers?
What would your engine sound like if it was pure stock with headers and glasspacks (lets assume it's an SBC).


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