exhaust drone/harmonic resonance

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340 swing

340 swing

340swing
Joined
Nov 6, 2008
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Location
Oxford Ct.
Here is what I have. Stock exhaust manifolds (70 340) TTI down pipes, TTI X pipe, Had dynomax super turbos took them off and tried spintech sportman 3000. TTI over the axle tail pipes and TTI tips. The car sounds great from the outside. But inside it hurts your ears annoying resonating just want to jump out kind of noise. I talked to Ron at spintech and he suggested trying resonators in the tail pipe area. There doesn't seem to be enough room. Has anybody had any luck with this? I have way too much money invested in this to give up on it, any ideas would be appreciated.
 
Doubtful you can get enough resonator on the A-body to cut out the resonation the Spin Techs create. They sound cool but like other chambered mufflers, they are not as driver-friendly as they could be.

We are playing with the new DynoMax VTs mufflers and so far, the two cars we have had them on sound good and do not show signs of terrible resonation. Will have more data just as soon as we get new tailpipes from Waldron. These will then be permanently mounted on a 360, 68 Barracuda coupe.

Tom
 
Thanks Tom, I would hate to take all of this off and end up at a local midas but the noise inside sucks. let me know how you make out. Somebody on here said accurate exhaust makes a muffler that works but I'm afraid to get them and have it not help. This is getting expensive.
 
Iron mike the drone was so bad with those I could not stay in the car. From what I've been told it depends on the set up ie: the engine specs that control the drone. The spintechs sound real cool and helped the drone but not enough to drive the car anywhere far. Going to a local cruise or something no problem. But if you have to spend anytime in the car you will go deaf.
 
My Dart seems to have the same drone and it occurs on or about 1900-2000 RPM. I haven't found the solution yet. 3:55's and 14 inch wheels seem to keep me out of that RPM range for the most part lol. I'll be interested to see if you find the problem.
 
A good three pass muffler like Walker makes should quiet your car nicely. I have a set on my 68 GTS. Sounds great.
 
What type of walker mufflers are you using? I wonder how they would sound with my set up. Either of you running a Xpipe?
 
My truck does that and drives me crazy, but on mine its the high flow cat. convertor that causes it and being right under the cab doesnt help either. I was looking at mufflers somewhere (summit maybe) and they specified which mufflers would/wouldnt cause the resonance inside the vehicle.
 
I don`t remember what Walker muffler it was that went on my Dart because I had my muffler shop do the install. If I remember correctly though the outlet is a fraction smaller than the inlet if you use the factory size tailpipes. I did have an H-pipe installed which may have helped with resonance in the cab some.
 
I was just going to start a thread about the same thing. In my case it's a 360, 340 manifolds, TTI 2.5" H-pipe with Dynomax Super Turbos. From 1500-2000 rpm, I feel like one of the aliens in 'Mars Attacks" when their heads explode.
 
Sound deadner under the carpet rear seat helps a lot.

My 1964 Valiant, and other cars I have owned had No carpet or padding under the rear seat. The mufflers are right under the rear seat,
and the sound echos into the car.

Here is a good place for sound deadner.

http://www.raamaudio.com

headlinerproject64Valiant026Small.jpg
 
I also put in the sound deadner and bought some 1/4 closed cell foam to put under the seats. All this made a difference but did not eliminate the drone. Dusterglen try to talk out loud when you hear the noise it reminds me of talking into a fan when i was a kid. I also have a 360 in my car but an x pipe. I have a lunati cam, air gap intake and edlebrock carb.
 
I have found on different cars that placement of a resonator makes a big difference on eliminating the dreaded drone.
Try adding a couple of short resonators 12" in front of your mufflers and see if this fixes it.
 
My previous exhaust was patched together from a bunch of leftover pieces. Severely abused Hedman headers, rusty 2.5" front pipes into polished stainless Borla Pro XS mufflers and stock replacement tailpipes. The tailpipes had the crimped bends and funneled down from 2-1/4 to 1-7/8 at the tips. It looked like a total hodge-podge, but except for all the leaks, it sounded better than my good looking expensive system. Man, I hate muffler trial and error.
 
I ordered my TTi exhaust in December and the Dynomax mufflers I got seemed waaaay too quiet. I ALMOST started the trial and error thing. I decided to wait until spring and "break 'em in".

I'm glad I waited. They seem real......classy is a good word. Not loud but the tone is just right. Nice, impressive, rackety-rack at idle and open up under throttle.

I too have a bit of droning. I'm running 4:10 gears and 55 MPH is good, 60 is very irritating and above that it subsides. My thought was the entire system, from headers to tailpipes, is rigid mounted. Ain't no rubber anywhere!

I plan to replace my 39 year old carpet and put in some sound deadener over the winter. I'll just live with it for now. Not a daily driver, so for me it's not a big deal.
 
My 383 Dart has Schumacher Tri-y's flowing into two Flowmasters that dump right before the axle.

I had a bit of a drone @ 2000 RPM, so I had a "H" Crossover installed.


Drone is gone. 8)


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No personal experience with fixing drone but ive heard muffler placement cant affect it, i.e. put the mufflers as far back as possible, but we all know thats near impossible on these mopars.

have you tried cherry bombs? nothing like a glass pack! haha ive always had flowmasters on my small block mopars but my brother put some glass packs on his 65 valiant 273 that exit in front of the rear wheels and it sounds friggen sweet so that is what im doing next.
 
i have the same drone on mine, 451 stroker, headman full lenght headers, 3" pypes into an x-pipe and flowmaster 40 series dumped before the rear axle.....i was told installing tailpipes would help, but i am not sure either
 
Does everybody with the drone on this thread have an automatic trans? This is my first automatic car and the only one that has ever had a drone. Just a thought. I would be curious to see.
 
I have hedman headers going to an X-pipe, going to thrush non turbo's, (flowmaster 40 knock offs) and have turn downs before the rear axle.

I get alot of drone at idle more than anything and some annoying drone pulses at cruising speed but it sounds good under load.

I have a 4 speed trans, and the whole floor covered with dynamat.

I had long resonators only installed before the X-pipe deal and dumped mid vehicle, and did not have any drone at all but it was loud.

There seemed to be a concensus in my other thread I posted that chambered muffs add to the drone as well as turn downs before the axle will bounce the sound up into the car to rattle your teeth, it makes perfect sense.

I am going to bring the exhaust all the way to the bumper to see how that works, if it still sucks I will have to try another muffler.

From what you described, your car is doing exactly that of mine.

Also make sure your exhaust is not bumping up against the floor in any places, and let us know how it works out if you get yours fixed before me. LOL.
 
I have the Summit 2 1/2" kit with their mufflers and manifolds, 69 340 727 4.10 rear, a little bump to the cam....450 .455 268/272 durarion No H or X pipe yet. Full 2 1/2 tailpipes to the rearbumper with the repop 2 1/2 tips. Very bad drone at 1800 rpm. The funny thing is that at 2300 rpm, the exhaust is so quiet that I can wisper and carry on a conversation. 3600rpm drones nearly as bad as 1800

I was gonna swap in the Dynomax super turbos, but not after reading this thread. Looks like the new dynamax mufflers are the answer.
 
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