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quiet mufflers upgrade ?

25K views 76 replies 28 participants last post by  NickeyChevelle 
#1 ·
509 bbc
780hp . currently running 3 inch xpipe 3inch xlerator mufflers [18 inch case] then 2 1/2 tail pipes over the axle out the back.i want to change tailpipes to come out behind tires ,car is a 66.to look more stock.Is there a quieter muffler i could use ? Do i need 3inch tailpipes ? tia
 
#2 ·
Been researching this quite a bit recently. This site doesn’t seem to have any love for Flowmaster mufflers.

I just picked up a used Torque Tech 3” system with 70 Series Big Block mufflers.

Fortunately, the system also has cutouts so I can see if the mufflers are costing a ton of power.

If I was looking for new, I’d check out the Flowmaster 55 Series Big Block Mufflers.
 
#4 ·
Walker turbo 17665....22" case..3" in/out; you can adapt the 2.5" tail pipes. I think the 17749 is the same muffler; different number.

There's also a Walker 17236..24" case; they fit fine under GM A-body... these are 2.5" in/out, BUT.., Walker specs show these flowing more than the 3" pieces I mentioned above..

As to whether you need 3" tails...endless debate, but I'd compare 1/4 mile MPH with 2.5 and 3"..that'll answer your question.

I have the 17665 on my 540 with 3" tails/behind tires;..Once you're 200 feet down the road at WOT, they're pretty quiet from outside. I am going to try the 17236 sometime next six months to see noise levels and try to get some mph numbers..

Bob
 
#5 ·
There is a guy who races a 70 Chevelle SS with a 540 that runs high 9's and the car is quiet. He uses 2 spintech mufflers and 2 walker 3" bullets back by the rear fuel tank area. This sucker is quiet.
 
#6 ·
:cool: "A chain is only as strong as its weakest link." Unless there's some strong evidence to disprove it, I'd have to think that stepping down to 2 1/2 inches at the tail pipes is negating the effect of the large diameter of the 3 inch head pipes. Sort of like someone failing to use mandrel bends in the pipes. Your pipes are only as big as your smallest pipe diameter the exhaust gasses have to squeeze through.

Where mufflers are concerned: 3 inches in, 3 inches out.

Having the exhaust exit "behind the rear wheels" is not the best place for perceived interior "noise." Having the exhaust exit all the way behind the rear bumper would be quieter (in the passenger compartment). When my 'Bu's decibel level surpassed The Wife's approval level I added a pair of (straight-through Cherry Bomb) "glass packs" as resonators -- that helped reduce the decibels a byte. Ultimately, I did replace the mufflers. Strangely (surprisingly), I achieved a significant reduction in loudness by re-tuning my Holley following Holley's guidelines. Now the 'Bu runs great and is sufficiently not loud that The Wife no longer complains (… about the "noise" anyway).

Rest assured that when The Wife's not in the 'Bu, the loud pedal is still loud!
 
#10 ·
3 inch Dynomax Stainless Steel case Mufflers #17546 20"case with X pipe and 3 inch over the avels tubes. As for flow, they are straight-through 3-inch pipes. They are most likely one of the least restrictive mufflers on the market. Before this I ran Flow masters. Never again. I was replacing a flowmater muffler about once a year. Either the inlet or outlet tube broke at the welds or the baffle plates in the case came loose and started vibrating around.






They are quite inside the car. Below is a trip with the driver's window half open.



 

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#11 ·
Longest case turbo you can find such as 540 Olds listed
Hve the same Ultraflows as posted above..they sound great, quiter than youd expect but still loud

The 17665??? Above I believe doesnt neck down internally like some of them do
Box is buried in the garage so I cant check

Its for the Dodge Durango, 3 inches in/out offset offset not sure the 17749 is made anymore. I was told yrs ago little by little that line will be discontinued so have them "in case"

Mufflers are kind of apersonal thing, put on what sounds good and dont worry about minute power differences.
Hey if your fav was 15 less just get cutouts? Gotta like it when you turn the key
 
#12 ·
I have the Dynomax 17665 mufflers on my 69 and full 3" exhaust which is a little too quiet for my taste but very nice cruising around with passengers.
 
#23 ·
The 17665 is definitely the best if you want quiet and performance.

Of course they are louder than stock but much quieter than the straight through mufflers.

They do not "neck down" inside- they are 3" all the way through.
 
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#13 ·
3" out the back with cut outs, Dynomax 22" straight through mufflers, 454 manual trans 4K lbs. Back to back, hot lap closed vs open 11.56/11.54 do not remember the MPH...
 
#16 ·
I have pypes race pros on my 5.0 dd.
Quiet enough to have a conversation using 3" tailpipes, performance wise it trapped 116. Mph in the 1/4 mile corked up.
When my ambition grows I'll dropped the pipes and see what power they cost me.
 
#17 ·
I'm running one of the biggest mufflers I can find without tail pipes, the Walker SoundFX #17197..
https://www.summitracing.com/parts/wlk-17197/

Sorry, I haven't tried it yet so I have no experience. I am running the Dynomax Super Turbo 17749 muffler now and my 454 is quiet..

The exhaust gurus say you can run 3" out of the manifold then smoothly switch down to 2-1/2".. The Hooker #11135 reducer looks like it would work if you want to go this route.. Those reducers look like they would make cool tail pipe tips..
https://www.summitracing.com/parts/hok-11135hkr
 
#18 ·
jpvelle-
No one sells 3" tailpipe kits that exits behind the rear wheels, and only Flowmaster offers tailpipe kits. Pypes and MagnaFlow do not, they don't split their systems up. The FM kit exits out the back, BUT, it's a 2-piece tailpipe so you could have piece made to exit behind the wheel. https://classicmusclecarexhaust.com/p/flowmaster-prebent-tailpipes-3-rear-exit-flo15818


The advise you've gotten about Dynomax mufflers is spot-on. An Ultra Flow can easily handle your 780 HP and be fairly quiet too. 800+ HP F.A.S.T. cars use these with a 2.5" X-Pipe system and go low 10's/ high 9's. https://classicmusclecarexhaust.com/p/3-dynomax-ultra-flo-mufflers


As far as needing a 3" tailpipe, a 2.5" is probably adequate for the street, even at 780HP. I assume you open the headers at the track so no big deal. Gasses have cooled by the time they reach the tailpipe so pipe diameter isn't as critical. Remember, factory LS6 systems had 2" tailpipes, and even Hemi's used 2.25" tailpipes. The other benefit is that 2.5" tailpipes are quieter than 3".


Many people run a 3" system with 2.5" tailpipes with good results. However, I don't know for sure the HP and RPM level at which they start restricting power. I don't know of any dyno tests performed on various engines to determine that either.
 
#19 ·
JPVELLE/Jim asked "where did I find specs"

I checked Walker site and NO CFM ratings, so I called because I KNEW I had seen it. Tech told me Walker does not rate muffs in CFM...Told me to go to Dynomax site; I didn't know they separated company brands like that, but below are links to the 17236, and the 17235, which is the 3" version...
Both claim 2,000 CFM and up to 2,000HP, so I guess I need to add 1300HP to mine to get full use from muffler.??

HYDRO462 mentioned the 17197; GREAT price at $25 on Amazon, and light weight, but I could not find CFM rating because it is a "Walker" part; Tech told me they were designed for Ford vans in 1970-80's... He said the larger case would make them quieter, but had no idea/guess on actual CFM ability..

17236 2.5" Ultra Flo? Welded - Offset / Centered Muffler - P/N: 17236 - DynoMax® Performance Exhaust

17235 3" Ultra Flo? Welded - Offset / Centered Muffler - P/N: 17235 - DynoMax® Performance Exhaust

Muffler searches/results are like stumbling around in a dark room with very little light...There's always the "plan-B" Thrush-Hush, Cherrybomb glass packs, or "penny-spacers" instead of collector gaskets!!

As I get older, I don't want 'em to hear me coming; just see me leaving..

Keep us updated on what you use and how they sound/perform..

Bob
 
#21 ·
I have a full 3" Magnaflow stainless steel system on my car and I find it much too loud. :( It has two 3" mufflers under the rear seat and I've always wondered if adding a crossflow, transversal muffler behind the rear axle would help?…

Claude.
 
#22 ·
I have a full 3" Magnaflow stainless steel system on my car and I find it much too loud. :( It has two 3" mufflers under the rear seat and I've always wondered if adding a crossflow, transversal muffler behind the rear axle would help?…

Claude.
If you have a Chevelle, A transverse muffler is not an option. Dynomax Super Turbo's would be your best bet.
 
#24 ·
There are 2 case sizes for Walker/dynomax mufflers. The smaller case (4.x" x 9.x") will neck down to 2.5" tubes internally. The larger case (5.x" x 11.x") maintain a true 3" internal tube all the way thru. This is for 3" mufflers only

Sent from my SM-T817V using Tapatalk
 
#28 ·
Had FLowmaster 70 Series behind the 540" m was definitely restrictive but fairly quiet. Swap to Pypes 18" Race Pros was worth 5 mph (119-120 to 124-125), so yes, you can see the difference. On the street was a moot point, even choked down it was still too much motor for street tires. An X-pipe along with the longest case straight thru (Magnaflow 12578) flow real good and is quiet - and sounds good.
 
#33 ·
Had FLowmaster 70 Series behind the 540" m was definitely restrictive but fairly quiet..
I just picked up a used Torque Tech system with the 70 Series Flowmaster Mufflers, I’d have to say, I’m impressed with the sound.
It’s a nice deep tone and unmistakable Flowmaster sound when you crack the throttle. .

Easy to chat in the car.
 
#31 ·
The Ultra flows are not what Id call quiet...ask them about the super turbos they sound exactly the same but way quieter
Longer the case the happier youll be!
5mph is a huge difference from the FM by the way, wow.

I bet there is room to put a transverse muffler on that 71...most Ive seen with 2the long case super turbos are pretty darn tame.
 
#32 ·
I ended up with some borla 2.5, 14 inch case. Only bought them cause I got them for 20 bucks a piece, you can see straight through them and I though they would be crazy loud, but somehow they are quieter than the dynomax turbos that they replaced... sort of. They are quieter at idle and cruise but at WOT they are louder than the turbos. Never would have bought them because of the high price but they are well worth the money.
 
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