REPLACING FLOWMASTERS

Mine has flowmasters, 3 inch pipes and exit behind the bumper. No drone here. I would think exit and mounting has more to do with drone than brand of muffler.

Mike67 said:

We have them on the 55 too, turn downs in front of the axle , I love the sound...but there is a certain rpm i think around 1100-1300 rpm that the whole cabin will resonate enough to knock any fillings out.

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When I bought my Barracuda, the previous owner had 2 1/2" pipes coming back from the Tri-Y headers, through a pair of Flowmasters, and dumping right in front of the axle. Sounded good ( I like the Flowmaster sound) but I had the same drone you described in the 1200-1500 rpm range. It was fine at higher rpm's out on the road, but slow rolling through parking lots or slow traffic that was exactly how you described.

I replaced the whole exhaust system with 2 1/4" pipes through Magnaflows and out the back. No more drone. It doesn't sound like it did with the Flowmasters, but I didn't want to risk spending the money to put new Flowmasters in and still have that nasty drone, so I switched. Don't know if it's the full exhaust or getting rid of the Flowmasters that eliminated the drone, but it's gone.

Cornpatch MO said:

I don't understand this Flowmaster " drone " so many talk about. We drove our 440 engine Dodge 691 miles a couple weeks ago. Super 44's with 2 -1/2" exhaust pipes , 2 - 1/4" tailpipes, stock Magnum ex. manifolds. X pipe. Boom mat and heat duct insulation under the carpet. 2250-2500 RPM. No harsh sound at all , loved it--no reason to ever change it............MO

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Its like Mike67 stated, its the perfect combination of RPM, exhaust, pipe size, muffler design, etc. Each car can be different depending on the equipment - engine, gearing, exhaust system componet design. Some people will never experience the "drone."

My Pontiac G8GT, for example - mufflers were like WWII gerry cans - huge. Those prevented the dreaded drone when the engine would go into Active Fuel Mgt. (cylinder deactivation mode). Switched the cat-back to a Magnaflow, huge drone, would give you a headache. Switched to Corsa cat-back, huge muffler design, no drone.

I agree with your approach to insulation. Products like Hush Mat and DynaMat can make a huge difference in not only sound attenuation, but keeping heat out.

Boy, thanks for all the input guys! Lots of options to think about. To answer a couple of questions, I have full tail pipes that turn down at the bumper. The system is properly supported with hangers & nothing touching. Drone most noticed around 1500 rpm and gets fairly quiet above 2000 rpm. I think I'm noticing it more now because I'm running with windows rolled up (wife gets cold in the evening) but, in the heat of summer I go full "hard topping mode" with all windows down. Anyway, thanks for the help. We've got a really good muffler shop here that I'll check with & see what they can do.

I googled Helmholtz resonators ( another potential way to go ) and my phone sent me: Jones Exhaust turbine resonators, 2 1/2 " in/out,stainless,10"body ,14" oal,$31 at jegs. I'm sure other sizes are available. Might be cheapest and easiest solution. (Jegs part #523-JR25)

I'm using Flowmasters on my Firebird and either I'm deaf (I am in one ear), but I've never had any issues with them. Headers to 2-1/2 pipes to mufflers and 2-1/4 tail pipes out the back.

I'm using glass packs in my Mopar.

IMO tail pipes that do not go all the way past the rear bumper, are going to be louder to people inside the car. The floor will be like an amplifier. Echoing the sound waves between the floor and the road. Turn downs will probably be louder because they direct the sound waves toward the road. .............MO

I've managed to completely remove all resonance/drone from my '69 Charger. It was a long process and I tried several different solutions but only one worked 100%. When I first bought the car it had Flowmaster 40 knock-offs and although from outside it sounded amazing, the drone/resonance inside between around 1700-2000 rpms was unbearable. Since I drive the car a lot, I had to find a solution. I tried Dynomat on the rear floorboards with no results. I then replaced the "Flowmasters" with Dynomax Ultraflows. This helped a little, but I think it had just as much to do with the reduction in overall sound as anything else. I then had my exhaust tips extended to move them out past the bottom of the bumper. No difference. I then installed a set of QTP electric cutouts and this helped somewhat, but it was still present enough to want to continue to try and improve it. I finally read about the Helmholtz resonator idea and decided to give it a try. You first need to determine the frequency of the drone, so I took a quick video on my cell phone and played it on a free frequency analyzer app and found out the drone was (IIRC) 125hz. Based on this the resonators needed to be around 26.5" (again iirc) and I had them mounted (not welded) to the y-pipe I was using for the cutouts. I had my exhaust guy fabricate them to fit properly. This did it and COMPLETELY removed the drone. It was just in time as I was planning to participate in a car cruise (150 miles or so) the next weekend. It couldn't have been more enjoyable!!!
The downside (besides losing the cutouts) is that the resonator removes the corresponding frequency completely and overall the car is a little quieter. Since then I have many compliments on how great the car sounds, but I know it could be louder. I'm thinking of switching back to the Flowmasters and see how it sounds. I may have to tweak the resonators, but we'll see.

moose1 said:

Ok, so my '66 Poly 318 has a nice set of flowmasters on it. Sound great from the outside, but the dreaded flowmaster "drone" is wearing a bit thin. Soooo, I'm contemplating changing them for something else. Here's where you guys come in....what would be a good replacement that still sounds good from the outside but quieter on the inside? I already had an H pipe installed a couple of years ago with little difference. I'm thinking magnaflow or something similar. Any suggestions? Thanks guys!

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look at accurate exhaust guy has mufflers that are hemi muffler size just put two on. They are magnaflow mufflers and are getting more rumbling after couple tanks of gas

66383 said:

What is the part # on your Borlas? Sounds sweet!

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Thanks. Here is the link from Summit:

https://www.summitracing.com/parts/bor-40359

Thanks..love that sound.