Correct but my custom stainless exhaust system is already fabricated and I'm trying to stick with similar mufflers it was made for.
CK5
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My quest for quiet, free flowing mufflers
- Thread starter Shawn
- Start date
I have Borla XS Pro or whatever there called on my Tundra. I had 5" tips and it sounded GOOD. It wasn't loud tho at all. Even under load pulling a hill or hard acceleration. The tail pipes have since rusted off, the mufflers still look good could they are stainless. I have some dumps on it now, maybe 1.5" long or so with turn downs. Can't really hear it at idle, dam fan makes more noise. Only time they were loud, actually more annoying, was when the tail pipes were off, then it was running right off the mufflers. Had pretty good drone pulling a hill.
I read from multiple sources the 3" Borla XS have a pipe that necks down from 3" to the internal 2-1/2" inside diameter of the muffler, and the same on the outlet. Want to stay away from anything that necks down in the muffler.
Sharp lookin exhaust and I’d have a hard time cutting it up for new mufflers.
FWIW GM necked the exhaust down on the late 1 tons at the muffler. 3" in, 2.75" out.
I've not found an easy way to calculate the diameter needed based on distance from the engine. But it is a thing to go smaller as you get further away from the engine.
Numbers I've found are 679hp for dual 3", so that far back, with that much margin, flow should be of minimal concern.
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I put em on 5-6 years ago, so don't remember what the insides looked like. They are quiet tho, but do sound throaty when you put ur foot down.
I don't think anybody can compare their exhaust setup unless it's dual 3". That is way louder than the dual 2.5" or single 3" that most of our trucks get set up with.
When I built a single 3" for my Buick I went through a few iterations before the noise level was tolerable at all. In addition to the biggest resonator that would fit (26" long IIRC), I ended up with a dynomax VT as the only thing that wouldn't drone. Unfortunately, those aren't as quiet at high RPM/WOT.
When I built a single 3" for my Buick I went through a few iterations before the noise level was tolerable at all. In addition to the biggest resonator that would fit (26" long IIRC), I ended up with a dynomax VT as the only thing that wouldn't drone. Unfortunately, those aren't as quiet at high RPM/WOT.
phreddei166
1/2 ton status
I use headers 2.5 inch pipe, dual Flowmaster 70’s. Quiet at idle and cruise, louder at heavy throttle.
I have a bbc tall deck 4.5 stroke. Its fkn loud. Thrush was the quietest and best sounding on my motor . Haven't tried the dynomax. I did try flowmaster 50 and that big as flowmaster bbc muffler.
Look up the Hooker Aerochamber. Does not neck down and is pretty darn quiet at idle and cruise. Center in center out could literally drop the 3" pipe right through them. If you get offset inlet it won't hurt the flow because of the internal design. I think for this situation you might like them. Either that or Borla straight through but they might be louder at idle and not as loud as WOT would be my guess.
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Subscribed for when my warranty is up.
What mufflers are you running on your 489 Heath? The Hookers?
I have the flowmaster 70 on my SBC K10. It's a dual 2.5 in and a single out. Really happy with the tone at idle, cruise and wot. Picking mufflers sucks.
On my 489 I have the "Big block 50" series, its bigger than the 70 series. Biggest quietest muffler flowmaster makes, it's about a 1ft wide and 2 ft long per side with multiple chambers(dual 3") and 5" thick. I like the sound of the flowmasters the best, but I think the straight through Borlas make more power. I think the Aerochamber is in between. Part chambered and part perforated, but no packing to blow out, should last nearly forever and is pretty darn quiet at cruise and low throttle. But does get louder at WOT. A good compromise.
I love my Flowmasters but I often wonder if I am giving up a few ponies with them.
Borla puts stainless packing in some that won't blow out like fiberglass, but they are really expensive.
As for dual 3", you'd be surprised. I had a ~425 hp hydraulic 388 SBC that I had dual 2.5" on. And when I opened it up at the track to the open long tube headers I would gain about .2 seconds and 2 mph, which about 20 hp at that performance level. My point is, dual 2.5 is not as good as you think if ~425 hp needs dual 3" to be optimal. I think dual 3" might be good up to about 500 or 600 HP.
This is the Hooker...
https://www.holley.com/products/exhaust/mufflers/parts/21505HKR
It appears they don't make the muffler I have any more, it is a 3" IN/OUT and they only make the "Big Block 50" series in dual outlet or 3.5" outlet now. One could make it by tapering down this one...
https://www.holley.com/products/exh...ered_mufflers/50_series_big_block/parts/53553
I have the same Flowmaster 50 series as @folkenheath on my 454. It sounds good, but definitely quiet. And that muffler is HUGE. It's a tight fit between the frame and driveshaft in my crew cab.
My stock 350 with stock manifolds into a y pipe 3" cat 3" magnaflow 3" out the rear had miserable drone. I had the 3" tailpipe reduced to 2 1/2" huge difference.
I realize you have a BB with horsepower I do not. But I was surprised how much of a difference the pipe diameter changed the drone and loudness.
I know this is not apples to apples but I wish I had known the effect of different diameter pipe and drone noise before having my exhaust built.
If you find a better/quieter no drone free flowing muffler without changing the diameter please let me know for my reference.
Good Luck
My stainless fabricator does great work with the TIG but I don't mind having him modify something if its going to sound better. I'll have him do some 3" v-bands on both sides this time which might make it easier to replace the next set of mufflers if needed.
If it necks down a little, thats fine but I just didn't want to go with something thats dual 2.5 muffler that restrict. Another thing I might do down is forced induction which means I need a good free flowing exhaust. Thats the biggest reason I did dual 3" and not 2.5"
Ok good to know. Thanks!
You are correct. If I had a single 3" with a more stock like engine, my Magnaflow would probably be fine. The cam it has seems to lope a little causing a fair amount of loudness. I don't mind a little at idle, just need to remove the drone and rasp at high RPM. It literally sounds like I have some Cherry Bomb glasspacks. And yeah, the bigger the body of muffler, the quieter it will be so I'm trying to find some big uns!
Ok good to hear. I was considering those or the 50 series. I thought the 70s were the quietest but from reading below, maybe not.
I looked into Thrush but the turbo mufflers didn't have the horseshoe thing the super turbos have for flow. How did you like the flowmaster 50? Loud? Quiet?
I looked those up and watched some videos of cars with dual exhaust and no cats. Seems a little loud from what I watched. Lots of these cars have some big cams though which I'm sure is not helping with being quiet. I wish there was a standard decibel test on every muffler produced. Idle and WOT test.
Ok good to hear. I think the single itself REALLY quiets things down which I can't do unless I want to change the entire stainless exhaust I just built. The dual 3" exhaust will make any muffler loud.
Great info. Thanks! Eventually I will have forced induction weather it be a supercharger or turbo. I realize the headers will have to go with the turbo idea but I didn't want to have to change the entire exhaust for any FI upgrade. Might as well go big to begin with. Anyway I will look into the flowmaster 50 bigblock. I do agree they aren't the best for flow. I've seen dynos with flowmasters compared to other mufflers and its not that impressive. That being said, I'm more worried about making quiet now so if I have to give up some tq/hp so be it.
Good to hear. I think I can fit them. My current mufflers are 24" body and 28" in total length. Thanks!
Thanks !I USE to have a big block but went back to a 406 SBC. My initial goal was twin turbos and make some killer HP with this Dart Block/AFR combo but had to scrap the idea after we signed on a new house build and I had to hurry to get the project running so the turbo idea went on the back burner for now. I do realize the smaller pipe helps but would rather not do that since it would require to scrap my entire stainless exhaust system. I think there are some 3" mufflers out there that will help.
I did come across this old article from a Pontiac site.
https://pontiacstreetperformance.com/psp/exhaust.html
Shows the mufflers flow and sound levels. It is pretty old so some are not being made these days. But look at the 17749 Dynomax Super Turbo. Seems to flow well and is quiet. That would probably be the offset/offset design that looks to have the best flow internally.
