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I would like to get a mandrel bent system for my 67 GTS but all the ones I have seen are header back systems. I have stock exhaust manifolds. Currently using 2.25" to mufflers and 2" tail pipes. Muffler shops in area don't have expensive mandrel bender so custom made to fit is not possible.

I see the website to calculate tube length and show you all the harmonics is not valid anymore. So here's the equation Frequency (f) = Velocity of Sound (V) / WaveLength (Lw). Assume a working resonator temp of 50 degrees C (122 F): V is 1187 Ft/sec. So knowing the frequency and velocity of...

It works better to measure the drone frequency instead of trying to calculated it or experiment on tube length since is can be different. Mine was 125hz and another guy posted was 105hz. The thread gtxduded posted has information on the phone app to use to measure DB verses frequency and a web...

Interesting resonator. Problem I see is the tube length in the resonator inside may not be correct for some drones. Drone frequency can vary some from what I have seen from posters using the phone app I used to measure your actual drone frequency. On this page of my thread, Suggestions for...

Drone is a problem. I had a pretty good case of it. Muffler, H pipe, X pipe may help solve it and maybe not. I tried different mufflers including Dynomax VT mufflers that are suppose to control drone but they only reduced it 12db and it was still annoying. After my journey was done and what...

From what I've read people have installed them in front of the muffers with success. I would think as long as you ars elinminating the offending frequency it should be fine. Don't forget it's the entire length including the radius of the bend in your 31".

Mine use to rattle in my 1967 GTS Dart about 45 years ago. I tried fixing it and it still rattled so I took the spring off and let it stay open. Been that way ever since and haven't missed it.

The 90 I used had a flare you can see in the photo and it was long enough to allow some adjustment. You could also make a cap for the end the you clamp on to get some length adjustment. If you did both you would have inches of length adjustment to the length if you had to tune it. I don't...

I watched the video link you posted. He was talking about trying different resonators to see if it eliminated the drone. Trial and error is a lot of work when you can just measure the frequency at the rpm it occurs, calculate the size of the resonator, install it and your done.

Yes. There was a part of high school physics called wave physics where you studied waves and there interactions and you probably thought when would I every use this information. Here ya go this is it. :-)

I got the 90's and the straight pipes from Jegs or Sumitt to make mine. The 90's were a smooth bend that's one of the reasons I bought prefabed ones. I also used a slip fit on the pipe where it connects to the 90 so there could be some length adjustment/tuning possible. 2" tail pipes with...

Five years ago when the Dart was redone the body shop painted the exhaust manifolds. They are holding up good so I asked him what he used. He said POR 15 high temperature paint. Summit had it and says: "POR-15 offers several high-temperature paints that you'll definitely warm up to. If...

You can put branch resonators on the exhaust pipes which are tuned to the drone to cancel it out and keep your existing exhaust system setup. I didn't remove any of the exhaust system to install them. My drone was at 125hz and I took care of it by putting on the side branch resonators. Here's...

Drone can be tough. Same muffler on one engine and exhaust configuration drones but not on another configuation. I had stock pipe configuation with three chambered performance mufflers on the 383 with a cam that had stock lift, twice the overlap, Rhoads lifters and single plane intake with no...

A lot of factors come into play with drone. I went thru a whole journey of drone and different mufflers. I started out with an Accurate exhuast system with their chamber performace muffler on my 383 Dart. Had a cam with same lift and duration as stock but twice the overlap and no drone...

That is low. Lower than the common frequency for a v-8. Interesting. Is it vibrating any of the car like the rear view mirror? :-)

Thats great. I have a sister inlaw who lives in Palatine. Small world. I tell people for me loud exhausts are only fun for about 5 minutes. Longer drives need more tame levels and no drone. It's also nice to be able to have a conversation or listen to tunes too. :-)

Thanks for the update. Glad to here it worked out for you. Nice overlay

Mine don't rattle. A few times I heard them close when I shut off the engine but it stopped doing it. Since the drone is gone I'll probably put the magnaflows back on some day. Right now it's lower on the list.

Dynomax VT mufflers are not suppose to drone according to Dynomax. For me they reduced the drone 12db. There is a thread on my journey to get rid of my drone. Tried different mufflers the last being the Dynomax VT's. What finally worked for me was using branch resonators...

Interesting. I'm assuming it had something to do with changing the frequency a little and level between the two pipes so they didn't resonate. Wonder if this is a repeatable cause and effect. If it is you could just always do it when you change mufflers as a proactive approach for possible...

You might find this interesting. A guy put branch resonators on his Shelby Mustang with cutouts on the branch resonators so he could turn them on or off...

I tried strapping some steel weight to the tail pipes and it didn't make any differance. The branch resonators did. They were more work but it worked.

You are welcome. Let me know how it works out. I asked a muffler shop how much he wanted to install this once. This was a place that did custom work. Regular Midas won't do it. He wanted $200 and you needed to give him all the dimensions. I assume he would have welded it in place. He...

If you go here http://www.diracdelta.co.uk/science/source/q/u/quarter%20wave%20tube/source.html#.U0sfFVpOVaQ and use a 27" long 1.5" dia pipe connected to a 2" dia pipe you will get 125hz. You have to convert to meters for dimensions. You will get the following. Vertical axis is DB. Looks...

An amusing point is here you may have thought what am I going to use this stuff for from Physics class when they were going over wave physics. I used the phone app I listed in the thread. On a my S3 android phone you can do a screen capture. I also took the file off the phone and put it on the...

I had the same problem with drone. Tried different mufflers even the dynomax VT which is suppose to get rid of drone. It reduced it but it was still there just at a lower level. I finally eliminated it with branch resonators. Here's the thread on my drone journey...

Good luck on your search. I'll have to keep and eye out to see what you end up with for mufflers.

I went thru a journey with drone with my 67 GTS. After the engine rebuild with a milder cam close to stock I got a brain rattling drone. Same exhaust system as before. Tried Magnaflow, Dynomax Turbo and finally Dynomax VT which are suppose to be drone free but only decreased the drone 12db...

Years ago I put an Accurate exhaust system on my 67 GTS that has stock exhaust manifolds. It's 2.25" dia with 2" tail pipes. There seems to be some discussion about the original tail pipes being 1-7/8" or 2". I got my car when it was 1.5 years old and 16,439 miles. It had the smaller tail...