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Discussion Starter #1 (Edited)
New 96 SS B-body owner. Previously an 07, 08 Gen9 SS owner.
Looking for Exhaust advice on my 96: previous owner installed Borla catback Stainless system (muffler, resonator, H-pipe). On My 07, 08 SS's I did the resonator delete and Borla performance mufflers and it had a nice low growl to it but some drone at cruising speeds. On my 96, Although it’s a nice expensive exhaust, it has no growl and it’s a shame to waste the true dual potential. SO do I do a muffler delete or resonator delete and would the tubing size make any significant difference? I just want to get some low growl out of it without the drone and NO poppy crap.
 

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If you want no drone you will have to either have resonators or delete them and run the exhaust pipe so it don't point at the ground and doesn't end under the car.
Plenty of threads discussing this.

Some reading about how exhaust works

-ALF out...
 

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Discussion Starter #3
Thanks! Leaving the resonators is where I was leaning towards. So if I did just a muffler delete and left all else (resonator, H-pipe, tubing size) how drastic would that be? I don't want to be the obnoxious neighbor with the rattle-trap like the teeny boppers with the new mustangs and squat trucks.
 

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In 25 years I've NEVER heard of any tri-9 B-/D- with any drone using an intact complete Borla cat-back. If you've got the complete $1,200 2-1/4" Borla with resonators and a cx-over pipe, and you're not over 350hp at the wheels, well then I wouldn't touch a GD MF thing. Just IMHO. ;)

I HAVE heard one in person and agreed with others standing around that it's the quietest system out there. If needing some more manly noise though, why not try an experiement of something less drastic like drilling some holes in the tailpipe for a couple inches. If it doesn't do the trick then it's just a matter of a s.s. band clamp and copper RTV, and then you can start removing parts. Removing resonators on a car that don't drone plain sounds like tempting fate. If you choose that then strongly suggest doing it careful in case deciding to re-install.
 

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Discussion Starter #5
There’s currently no drone from the Borla system it’s just there’s almost no sound, It’s very quiet. On my 07, 08 SS with a single cat, by doing a resonator delete and Borla mufflers gave a nice growl but some drone. Since the 96 has true dual it would be nice to get some growl to it and wanted to know if doing a muffler delete and leaving the resonators would make it obnoxious.
 

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Yes it will be obnoxious, but i liked it and had it for years. Idle had Awesome rumble.
To me it literally sounded like the Gen Lee in Dukes of Hazzard when i got on it.

My car with muff delete first 10-20 secs.
-ALF out....
 

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Discussion Starter #7 (Edited)
Nice! Like that sound! So you did a cat back, muff delete, x-pipe, resonators (square box)? What tubing size did you go with and was it the same all the way to tips? Any change on the front end (Intake)?
 

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Okay DTW..... car history is in cardomain link in SIG.
google search "Angelo's" exhaust thread" for my setup.

1. ran stock
2. ran stock with muff delete
3. ran setup that was installed in vid and pics in thread i mentioned above for you to search for.
-ALF out...
 

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Discussion Starter #9
A
Okay DTW..... car history is in cardomain link in SIG.
google search "Angelo's" exhaust thread" for my setup.

1. ran stock
2. ran stock with muff delete
3. ran setup that was installed in vid and pics in thread i mentioned above for you to search for.
-ALF out...
Okay DTW..... car history is in cardomain link in SIG.
google search "Angelo's" exhaust thread" for my setup.

1. ran stock
2. ran stock with muff delete
3. ran setup that was installed in vid and pics in thread i mentioned above for you to search for.
-ALF out...
Nice write up! Are the rectangular boxes mufflers or resonators? And if I read it right, it's 2.5" all the way front to back? On the vid clip, is the 1st sound part with the muff delete and rectangular boxes or is that configuration sound at the very end of the video?
 

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Hi, Rev at start of clip is #2 rev at end of clip is #3
Spintech is mufflers, you can google them.
You see the resonators being cut off in the vid.

stock manifolds and cats, then 2.5" the rest of the way.
-ALF out...
 

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OP

if your motor is stock and you have a Borla exhaust and want a more aggressive exhaust sound than pull the Borla mufflers and install SpinTech Pro Street mufflers.

Personally I am not a fan of poser exhausts if the motor is not built as they never sound like "muscle" just loud and raspy. Especially straight pipe muffler and resonator delete exhausts.

Resonators keep the drone away during Fwy driving

Exhaust sound is subjective so what you like others may not and vice versa
 

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Bone stock Borla sounds decent outside the car when you romp on it. Before you tear it off, have someone do a standing 1/8th mile run with you standing outside the car and see if you like it first before you go messing with it. Borla engineered the system to breathe well on a stock engine while preventing drone inside the cabin. It's one of the nicest systems out there.

As already warned, these cars drone like crazy when you start messing with the exhaust. I installed an ATR Quad (no longer available) on one of my Caprices back in the 90s. It's a fully welded heavy-gauge 2.5" system from front to back with a H-pipe, blow-through mufflers and resonators. It sounded like a big-block at idle but droned like crazy even with the resonators they provided. I had to modify the turn-downs to exit straight out the back just to stop it from giving me a headache. They also sold an ATR Dual system which deleted the resonators. So as an experiment, I deleted the resonators for about a year when I was regularly racing it. Sounded good outside the car but the drone was even worse and my girlfriend at the time refused to ride in it. LOL. I still have the car with that exhaust... but back to running resonators again. I like the rumble at idle. But a stock LT1 with a H-pipe or X-pipe will always sound subdued unless you change the cam. Then things get fun.

If I built a new exhaust from scratch, I'd run 2.5 inch to the mufflers, then neck it down to 2.25" after the mufflers over the axle and out the back. This will not restrict flow because the exhaust has sufficiently cooled. Necking it down will also prevent some drone by increasing exhaust velocity. Using resonators would be quieter. Exit the pipes straight out the back, about 1" past the bumper (no turn-downs). A buddy of mine built a system like this for his '96 many years ago and it worked and sounded great with no resonators. I should have bought that system off of him when he sold the car. But I didn't have a spare stock exhaust to put back on to sell the car at the time. Oh well.
 

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Discussion Starter #13
So I did the muffler delete. The Borla Stainless is 2.25” from CAT to muffler then 2” the rest all the way back to resonator and tips. This stock system, although nice quality, had NO sound even under acceleration. So I inserted a 2” SS piece where the muffler was to keep the system all stainless and contiguous dia. Now I get a nice throaty growl under acceleration and a soft burble at idle. My limited previous exhaust experience with 07, 08 Gen9 Impala SS with single CAT then resonator then Y into 2 mufflers. I did a resonator delete and replaced with Borla mufflers. Both gave a nice throaty rumble but gave a little drone from 1.5k to 2k RPM regardless of acceleration or not. So my 96 SS I decided to try the muffler delete and leave resonators. Although a bit louder than the Gen9’s the drone is more acceleration dependent and not RPM dependent. Anyway gonna try it for a while, see if I like it and if not can weld the Borla mufflers back or try some that are more aggressive.
Thanks all for the advice and feedback.
 

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Cool. Thanks for the update. In my experience with drone on these cars, it's usually present around 2000-ish RPM (no matter how much pedal you give it). And gets louder with more gas or load in this range. This makes it terrible for highway driving because with 3.42 gears (or steeper) like I'm running, that puts you right in that drone spot at highway speeds. If your current system does not have this behavior, then you are ahead of the game already. Might just need some tweaks like you mentioned with different mufflers, that's all. Keep us posted.
 

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Discussion Starter #15
Again in my limited experience, empirical analysis appears that mufflers reduce the amplitude across the entire frequency spectrum and resonators are designed to reduce "certain" frequencies. So my results are that in the typical 1.5k to 2k RPM's if I'm at a constant/even cruise and not on the accelerator there's no drone. Soon as I get on it, the drone amplifies and then starts dropping off over 2k. Whereas my Gen9's gave a drone in the 1.5-2k range even at cruising, with it being a little louder under acceleration. I know that pipe diameter has an effect on that formula also, but why I left it the same as what was there and the only net cost was the 2' section of stainless 2" pipe.
 

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According to David Vizard, a 2.25” dual exhaust system is good for a 457hp engine with zero loss …

The vast majority of 350 & 355 LT1s would have a very tough time achieving 457 horse without an intense mod regimen. 383s & up, easy.

Obviously, Mr Vizard assumes that your 2.25" dual exhaust system has no meaningful restrictions, like fold- or crimp-type bends.
A perfectly mandrel-bent 2.25" dual exhaust is getting tougher to find, and is much more expensive than merely swapping in the 2.25" in&out mufflers of your choice plus ready-made 2.25" tailpipes.
Think this is the main reason why many go for 2.50" exhaust systems. That, and not enough good 2.25" systems left.

Another less-well-known drone solution that the ISSF has experience with, is to attach more weights to the exhaust system. The OEM exhaust systems Buick Roadmasters and Cadillac Fleetwoods are of course very similar to LT1 Caprice exhaust systems, but Caprice exhaust systems lack a few extra weights that Roadmasters & Fleetwoods have, specifically for additional drone resistance.

Beyond that, there is something that my terrible memory foggily recalls as a 'Buick Brace', which I think was merely a small piece of tubular metal that bolted to both rear frame horns, connecting them much as a tow hitch would. Although this is not terribly popular, a few of the people left here who autocross or road race their Impalas SS / Caprices have found that improving on the Buick Brace also improves handling responsiveness.
Obviously an actual tow hitch would also work, but may not be worth the aesthetic sacrifice.
 

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Thank you Thank you Thank you. I don't near often enough hear others commenting on the 'folly and lust' for larger exhaust. As you say, the -->real<-- issue is to replace the "nearly crimped closed" oem exhaust with a legit mandrel bent 2 1/4" setup. Which are getting tough to find. Below Borla's $1,200 price at least. Summit/Jeg (i.e. Heartthrob) has a respectable 2 1/4" non S.S. system, with quite decent chambered muffs. Since there's no more Hooker Aero-s anyway.

And I had not known the threshhold was 450+HP. I've been preaching over and over on here that 2 1/4" is good for up to 350hp, which BTW it's clearly and sadly obvious most posters considering them don't come close to with just their K&N filter and glasspaks with turndowns LOL

Interesting hearing about the weights. I keep them on all mine even after new catbacks. But, I always considered they were intended to reduce driveline torque twist on acceleration and keep blu-hairs in Caprices and FWs from getting scared.

As you say, for the rear brace I consider the hitch on my Cady works perfect for that. Some thread rod and Grinnel clamps would be a good hack if just intended to 'couple' the back horns together for drone.
 

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Quoting a post excludes previously quoted material inside it; the following is something I posted about a decade ago:

The Great David Vizard said:
Once the available flow exceeds about 2.2 cfm per hp, the gains possible by increasing muffler capacity drop to less than 1 percent.
… 2.2 cfm per horsepower …

A 2.75” Single is good for a 310hp engine with zero loss …
A 3.00” Single is good for a 370hp engine with zero loss …
(Why would the numbers for a 3.25" single be absent?)
A 3.50” Single is good for a 503hp engine with zero loss …
A 4.00” Single is good for a 657hp engine with zero loss …

However, each side of a Dual system only needs to flow 1.1cfm per horse, so …

A 2.25” Dual is good for a 457hp engine with zero loss …
A 2.50” Dual is good for a 513hp engine with zero loss …
(Why would the numbers for a 2.75" dual be absent?)
A 3.00” Dual is good for a 812hp engine with zero loss …

Oh, by the way …
The Great David Vizard also said:
The first misconception that needs to be cleared up is that a header relieves backpressure, but a certain amount of backpressure is needed for optimum performance.

Just the opposite is true.

A good header not only relieves the backpressure, but goes one step further and creates a vacuum in the system.
When the next cylinder's exhaust valve opens, the vacuum in the system pulls the exhaust out of the cylinder. This is what the term "Scavenging" means.
 
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The OEM catalytic converters are fine.
The OEM exhaust NEEDS the following corrections / upgrades:
free flowing mufflers - minimum 2.25" inlets AND outlets
free flowing 2.25" tailpipes that were not angrily bent by a really strong guy, even if it was bent around his thigh
free flowing 2.25" resonators to mitigate some drone
tips that point away from the ground

Not all 2.25" mufflers are free flowing. How many mufflers cite their flow numbers? How many mufflers even HAVE flow numbers? Answer: not enough, gottdamnt.
Not all 2.25" tailpipes are mandrel- or even crease- bent. Many are kink- or crimp- bent, which is actually WORSE than OEM.
Point is, even though a well-designed well-built 2.25" catback exhaust SHOULD be fine, I begrudgingly get why 2.50" exhausts exist for our cars - crappy bends.
 
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However, each side of a Dual system only needs to flow 1.1cfm per horse, so …

A 2.25” Dual is good for a 457hp engine with zero loss …
A 2.50” Dual is good for a 513hp engine with zero loss …
(Why would the numbers for a 2.75" dual be absent?)
A 3.00” Dual is good for a 812hp engine with zero loss …
I’ve also read a lot of Mr. Vizard’s articles and I recently put together a reference for myself since I’m planning my new exhaust. I think there might be an error in the numbers you have listed for the 2.25” and 3” dual exhaust numbers. It looks like the 457 and 812 numbers you have listed are actually the flow capability instead of the HP capability. Though (admittedly) 2.25” pipe is still sufficient for most of our cars at 415 hp.

I'll attach a screenshot of the chart I put together since I can't get the formatting to work out right in the text. If I'm mistaken, please correct me. I'd like to make sure I'm referring to accurate numbers.
exhaust_flow.JPG


Unfortunately, I didn’t find this info until I’d already purchased 2.5” mufflers and 2.5” pipes to fab my tailpipes. If I had it to do over again, I’d go with 2.25” for a little more clearance.

In the Vizard exhaust articles I’ve read, he seems careful to separate the headers from the rest of the system with a resonance chamber. If you terminate your secondaries with a chamber, then the rest of the system can be sized based on flow numbers only. If a chamber is not used, then your exhaust system effectively becomes an extension of your secondaries. This could leave a significant amount of power on the table.
 
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