ANNOYING EXHAUST SOUND

[CFD244]

Hi Folks

Just the facts Ma am'

1971 340 Demon.
Comp xe 262 Cam
Thermoquad Carb
727 trans with 2600 stall
3.23 gears
68-70 exhaust manifolds with TTI 2 1/2 inch exhaust......H pipe with turn downs.
Borla Mufflers

This thing sounds like you are blowing across a bottle top from about 1300 to 2300 (is this drone?). Sound is the same cruising at 40 mph, as it is at fast idle.

Once you get up to cruise at 50mph and 2500 RPM you can hardly hear it, and what you can hear is awesome.

No sound deadening other than what came from the factory.

I would really NOT like to add the chrome extensions unless they make a night and day difference.


Any suggestions???

 

[standup303]

Most exhausts I’ve ever had typically drone around 1500-2300. Can sound like an annoying hum, a buzzing, can get some bass in there too.

 

[RustyRatRod]

If it kinda hurts and annoys your ears, it's drone.

 

[CFD244]

Most exhausts I’ve ever had typically drone around 1500-2300. Can sound like an annoying hum, a buzzing, can get some bass in there too.

Yes.....Bassy. How do you get rid of it?

I paid big bucks for this system on a cruiser.......How do I fix it?

 

[RustyRatRod]

Yes.....Bassy. How do you get rid of it?

I paid big bucks for this system on a cruiser.......How do I fix it?

Different mufflers.

 

[lemondana]

Borla's are loud, sound nice, but loud. Cop magnets

 

[Oldmanmopar]

Scrap the borlas. They belong on a fart can import.

 

[Kendog 170]

I like quiet. Can't find that anymore. 3rd set of mufflers still a drone. I threw some cheap resonators in front of them and at least got rid of the drone.

 

[standup303]

Yes.....Bassy. How do you get rid of it?

I paid big bucks for this system on a cruiser.......How do I fix it?

You can try a Helmholtz resonator. Takes some minor calculations and some fab work but have heard great things.

You could install resonators like Vibrant which should but but may not completely eliminate the drone.

Different mufflers, something with a straight through design. A lot of guys use Dynomax Ultra Flows. I felt they were too quiet, but didn’t drone. Many others out there.

 

[abodyjoe]

68-70 exhaust manifolds with TTI 2 1/2 inch exhaust......H pipe with turn downs.
Borla Mufflers

where are the turn downs? at the rear bumper or before the axle.

drone is a *****. fox body mustangs use two different length mufflers to stop it. gotta find the right muffler that will stop it.

 

[CFD244]

Turn downs at the rear bumper.

 

[jos51700]

where are the turn downs? at the rear bumper or before the axle.

drone is a *****. fox body mustangs use two different length mufflers to stop it. gotta find the right muffler that will stop it.

Two different mufflers.... Interesting!
Is there a crossover?

 

[abodyjoe]

Two different mufflers.... Interesting!
Is there a crossover?

yes H-pipe

left muffler Part Details Page
Body Length (IN)
17.000

right muffler Part Details Page
Body Length (IN)
15.000

 

[abodyjoe]

left muffler Part Details Page
Body Length (IN)
17.000

right muffler Part Details Page
Body Length (IN)
15.000

 

[VOETOM]

Pontiac used two different lengths but they did it for cost reduction. The exhaust crossover valve negated the need for so much muffling on one side. This came from a former Pontiac Exhaust Engineer.

 

[AJ/FormS]

Mine cruises at 65=2240 (manual trans, in overdrive); quiet as a church-mouse...... until you stand on it, then, screaming all the way to 7200.
TTIs, dual 3" all the way, turn-downs, and TTI-supplied, Dynomaxers circa 1999. The hangers are also from TTI, big ugly dual-strap, rubberized things.
There are NO CLAMPS holding my pipes together.
At the front, they are slip fit. Both sides of the mufflers have ONE HH sheet-metal screw keeping them from rotating.
They have never droned, neither with the H-pipe nor after I cut it out. Not with near 200psi CCP nor with current 188psi. Not with any on the 3 cams I have run.
This car has run every gear ratio from 2.76s to 4.30s except 3.73s plus a few more, and has never droned.
And it has run every gearbox ratio, that Ma ever produced, and even an A904, allbeit with a factory stock 1973, 318.
No undercoat, no Dynamat, no back seat at all, just packing-felt lying under the carpet.
IDK;
I had a guy weld the factory rear floor-pan to the front pan. Anybody think, that might have something to do with it?

 

[33IMP]

Cheap glasspack, as a resonator, in the pipe where it's convenient (ahead or behind the muffler). May or may not kill the drone, will make it quieter.
Helmholz will kill the drone, but will probably need experimentation, or at least, math. Won't change sound or volume, j7st the drone.

Simplest, easiest solution? Change mufflers.

 

[CFD244]

The mufflers, unfortunately, have varying reviews. It seems that drone vs no drone opinions of the same muffler depends on who you are speaking to.......I never under stood how the same product could have a yes and no answer.

Did original 340 cars have this horrible drone? If not, what's the difference?

 

[VOETOM]

No 340 cars did not. The Darts and Cudas had very restrictive mufflers and had very small diameters parts of the system. They had carefully designed hangers too. This tends to make big differences. Even with the big chrome tips, stock ones did not drone. We had a 69 340 Swinger. I have a stock system for my 69 340 Barracuda. Very smooth and drone free.

 

[CFD244]

No 340 cars did not. The Darts and Cudas had very restrictive mufflers and had very small diameters parts of the system. They had carefully designed hangers too. This tends to make big differences. Even with the big chrome tips, stock ones did not drone. We had a 69 340 Swinger. I have a stock system for my 69 340 Barracuda. Very smooth and drone free.

Wow......Wish I'd never bought this system.

 

[VOETOM]

Borlas tend to be drony on old cars with no catalytic converters. They use only st. st. packing and that does little for certain frequencies compared to glass or ceramic fiber. Plus they are shorter (I bet). The factory Noise Reduction package used turndowns at the bumper instead of the tips so they won't fix it. With different mufflers, we saw lots of drone with most from 1800 to 2300. Like others suggest, time to scientifically tune it unless you can swap mufflers and add resonators.
PYPES sells a Turbo Pro that is likely less drony but not sure of your case size and configuration so not sure what number to suggest.

 

[1MeanA]

I'll have my Dart on the road this month. Its got manifolds, 2 1/2" TTI system with H pipe, FABO hated Dynomax mufflers and tips. We will see. I looked into this recently and thought I would try the Dynomax Flo Ultras if it didn't work out although I see these are still a straight through design. Perhaps a chambered design is what is needed?

 

[VOETOM]

Chambered tend to drone worse unless you have the factory triflow pattern. Ultraflos work well if the 20" long ones. The shorter ones are slightly louder.

 

[abodyjoe]

Chambered tend to drone worse unless you have the factory triflow pattern. Ultraflos work well if the 20" long ones. The shorter ones are slightly louder.

these are what you recommended for me a while back. Waker 17748 Super turbos... still haven't gotten a chance to order and install them.. you have anything quiet you can recommend or are they the best choice in your opinion?

 

[VOETOM]

17748s work very well but are 2" longer than stock A body ones. They fit though if you flange the rear and the tailpipes to make the install and removal easier.