Curing Muffler Drone - what muffler choice?

[73LemonTwist]

I have a stock '73 340 RR with custom bent 2.5" exhaust with X pipe (still using stock cast exhaust manifolds). I am having trouble finding a muffler that suits my ears. I have tried the Dynomax VT - wonderful sound at idle and no drone, but just too loud on the highway when its running straight through. So, tried the Dynomax Super Turbo. Quieter for sure, but it droned at 1500/2500/3500 rpm - especially when coming off the throttle. So now I have Flowmaster Delta 50 mufflers on the car. When not droning, they are reasonably good sound level. However they hit massive resonance peaks at 1200/2000/3000 rpm, especially when decelerating. My old ears can't take these peaks and they occur around your typical cruising speeds.

The mufflers are located in the same location as stock, just ahead of the rear end. The Xpipe is located under the tail end of the auto trans.

Suggestions on what to try next? I would like to have some of the old school rumble, but if I have to go super quiet, that would at least make the car more pleasurable to drive. Maybe have to go back to a tube/baffle style muffler?

Thanks...

Allan

 

[eric383]

If there’s room between the rear bumper and rear end you could try installing resonators.

 

[diesel_lv]

I do not know the standard mufflers that come w the TTI 3" full exhaust, but on my 496" w H pipe, it is quiet and I have no drone at all. Could have to do w me having H as apposed to X and 3" compared to 2.5". But I like my mufflers.

 

[topside]

Where does the exhaust exit ? I haven't had a droning problem on anything with full tailpipes, whether Flowmasters or Super Turbos. Exiting at the rear axle, they'd drone. On a 512" Duster with a 3" system & Flowmasters, it was horrible; but adding 2.5" tailpipes to the rear bumper cured that. X-pipes have been slightly quieter than H-pipes in my experience, and more efficient. Of the cars in my sig pic, the '68 has Super Turbos and is oddly quieter than the '69 with restoration mufflers. Both are otherwise stock exhaust. Might be because the '69 has more CR & a bit more cam than the '68, but both are basically stock. Resonators, as suggested, are another fix - they can be glass-packs or OEM-style.

 

[73LemonTwist]

The exhaust exits the rear through OE style tips like factory. I can see exhaust exiting under the car being an issue. My old '70 383 had Hush Thrush exiting before the axle back in the day and it was plenty loud...

I have wondered if the x-pipe could be setting up the resonance if its not the correct distance from the manifolds. The installer formed his own x-pipe when he was installing the system (rather than using a commercially available unit).

Have been wondering about going to a Walker Quiet Flow or Walker Mega Flow muffler - anyone have experience with these?

 

[PurpleBeeper]

I've been down this road. IMO, the only way to get rid of the drone is stock-type mufflers. You'll have to search to see what's available in 2.5". Walkers are relatively quiet, but are only available in 2.25" from what I've seen

 

[33 IMP]

The most elegant solution is a Helmholtz resonator. (Google it). But they take some fabrication, and some calculations that lots don't want to do. And Flowmasters are also known as dronemonsters.
If you don't want to change mufflers again, and if you have room along side the gas tank, I would try either specific resonators, or small glasspacks used as resonators.
If you don't have the room for add on glasspacks, I would go with the biggest walker quiet power that will fit under the car.

 

[68Moparmaniac]

Go faster...

 

[JoePole]

I have a similar set-up as you. Was running Flowmaster 40's with HiPo 340 manifolds. Added H-Pipe and moved the drone up to slightly higher RPM. Swapped to Dynomax Super turbos and no more drone but very quiet. Added headers and now perfect for me plus more torque.
I think the Walkers are going to be very similar to the Super Turbos. H pipe vs X may be the difference.

 

[rumblefish360]

The most elegant solution is a Helmholtz resonator. (Google it). But they take some fabrication, and some calculations that lots don't want to do. And Flowmasters are also known as dronemonsters.
If you don't want to change mufflers again, and if you have room along side the gas tank, I would try either specific resonators, or small glasspacks used as resonators.
If you don't have the room for add on glasspacks, I would go with the biggest walker quiet power that will fit under the car.

THIS ^^^^^^^^^

Is your answer.

 

[Ron H]

You will find tons of chat about this searching the forum. Tons. Muffler selection reminds me of reading a menu at a Greek restaurant. Had FM 50’s that sounded nice; but too loud. A few members suggested hemi mufflers pretty much a factory sound/level and went this route as I didn’t want to fork out for another set of mufflers only to find them too similar to what I had. MO, good choice, pretty quiet especially cruising. But, if you’re wanting some more sound, those might be a bit too quiet.

 

[AR67GTX]

I have TTI supplied Dynomax super turbo mufflers on my GTX and Accurate high performance Hemi mufflers on my 66. Neither have what I would call drone although there is some rumble at speed. The Accurate mufflers have a harsher idle sound with the Dynomax sounding mellower.

 

[73LemonTwist]

You will find tons of chat about this searching the forum. Tons. Muffler selection reminds me of reading a menu at a Greek restaurant. Had FM 50’s that sounded nice; but too loud. A few members suggested hemi mufflers pretty much a factory sound/level and went this route as I didn’t want to fork out for another set of mufflers only to find them too similar to what I had. MO, good choice, pretty quiet especially cruising. But, if you’re wanting some more sound, those might be a bit too quiet.

With the hemi mufflers did you need to add resonators? The walker SoundFX hemi muffler is a pretty good fit size wise to replace the FM delta 50, if I can get away without resonators at the tips.

 

[Ron H]

With the hemi mufflers did you need to add resonators? The walker SoundFX hemi muffler is a pretty good fit size wise to replace the FM delta 50, if I can get away without resonators at the tips.

No I didn't go with resonators

 

[Stroked438]

When I got my 68 Sport Satellite convertible it had some Summit mufflers on it and it droned really bad and was way louder then i wanted. I put a set of TTI headers on it 1 7/8 tubes with 2 1/2 pipe with X, Dynamax Super turbo with the larger 18 or 19 inch body, Flowmaster Flow FX mufflers as resonators after the axle. It is pretty quiet(thats what I wanted being a convertible) and zero drone. I have a exhaust shop at home for side work and bent everything my self so I can experiment with different mufflers but there is no need. When you stomp it all you can hear is tires and 4 barrel.

 

[Ron H]

Of all the muscle cars I’ve heard (and a few I had) having a stock exhaust, the RR/GTX was the best sounding of all, MO. Buddy had a ’69 GTX back in the day that sounded sweet, nice tone, not obnoxious, but enough to make a statement.

 

[73LemonTwist]

Headed down the OEM replacement hemi/440 muffler route. Ended up going with Walker Quiet Flows - 2.5" in and out. They fit in the space left by the Flowmaster Delta 50's, so no modification of the custom bent piping required. The ones I used were a "direct fit" part number for a mid '70's Cadillac big block. Got them on today and happy with the results - no droning and still some rumble at idle. Might even be able to hear the radio now...

Thanks for the help and ideas folks...

 

[Gary Gaz]

Headed down the OEM replacement hemi/440 muffler route. Ended up going with Walker Quiet Flows - 2.5" in and out. They fit in the space left by the Flowmaster Delta 50's, so no modification of the custom bent piping required. The ones I used were a "direct fit" part number for a mid '70's Cadillac big block. Got them on today and happy with the results - no droning and still some rumble at idle. Might even be able to hear the radio now...

Thanks for the help and ideas folks...

Any chance
on the part number pls

 

[73LemonTwist]

Any chance
on the part number pls

Walker Quiet Flow - 21856. They are 2.5" offset inlet, 2.5" centre outlet and 23" overall length. This muffler is aluminised steel construction not SS. I could not find a SS version with these dimensions. The rest of my exhaust system is not SS so wasn't worried about getting SS mufflers. (went with these mufflers as the stock hemi/440 mufflers I found were 2.25" in and out and a bit longer overall so not quite a direct fit for my application)

I also found a Walker Sound FX with the same dimensions - have misplaced that part number. I could dig it up again if you want it Gary. The local muffler shop suggested the Quiet Flow over the Sound FX from a construction and durability perspective.

The construction of these mufflers is such that the inlet and outlet tubes decrease in diameter fairly significantly for part of the tube length. You can see this on the cutaway views of the muffler available online - Walker website and others. I could see this when I looked down the tubes in an out of the mufflers before they were put on. Whether or not this affects back pressure significantly or not, I have no idea. Driving the car I can't tell the difference - except that now I don't need hearing protection, which was my goal... Thought I would point this out as many online reviewers seemed surprized/angered by this when they received their purchase.

I found the Walker website difficult to navigate and their filters hard to use. I found this part number using the screener on a popular performance parts supplier website.

Good luck

 

[sam dupont]

Resonators:

Classic Chambered Exhaust Inc. - Products