Need help with exhaust drone

70 Challenger 440 cr close to 10:1, Lunati Voodoo 60303 cam:
Drone from idle to about 2500 rpm. Almost unbearable low drone.
1-3/4 shorty headers, 3" x-pipe, 16" Dynomax Super Turbo's, 10 or 12 " glass packs along tank, standard rear valance so the pipes bends down about 30 degrees to get outlet under valance.
Rubber hangers, no interferance with body.

Strange thing: When we got the car it had a 512 stroker in it and the same drone, but only between 40 to 60 mph, not from idle. I then added the glass packs and they helped a lot but drone was still there.
After swapping in the milder 440 it got worse than to begin with. It will ring the ears from a low tone at idle and way past 5

All floor pans are covered with Dynomat sound deadener.

The Super Turbo's shouldn't be the worst mufflers. Do the shorty headers play a role? Or the down bends at the outlet? Or is it just a unlucky mismatch of parts?

Any ideas to fix this?

What is the ign timing set at & the curve, Vac advance ?

I bought a 70 Cuda 440 that had factory manifolds and 3 inch pipes. Drone was horrible. I replaced the exhaust with headers, 2 1/2 inch pipe and magnaflows.....no drone. I run the same Lunati 60303 cam as you.

In my opinion the biggest single contributor to your drone is the 3 inch pipes.

18 initial, 35 total. Starts at about 1000 rpm. All in by 2500 rpm.
No vacuumn.

bump it up 2 deg & see how it does

Pac is onto something, as I've done a similar deal adding 2.5" tailpipes behind some 3"-X-Flowmasters and the car got pretty pleasant, no drone.
That was a 512" Duster, TTi headers.
Also had a 406" SB Duster: full headers, 2.5", H, Flowmasters, tailpipes & tips, never droned at all, which is supposed to be impossible.
Droniest car I ever had was a wagon with 3" system, tried 3 different mufflers and the Dynomax Super Turbos had the least drone but there was still some.
That was 446" full headers, 2.5" tailpipes.
I think the wagon body amplifies any droning, so you may want to disregard that comparison.

An old trick is to put the glass packs on backwards. Guy at muffler shop said trust me. I did and don't know why it works but I did it on a 450SL years ago and other long time owners couldn't believe how quit it was.

Mike

I have a buddy with a 70 Challenger 440-6 car that went with a TTI 3" system with the 3" x 16" Super Turbos. Exhaust sounded great for about the first two years. Then, the fiberglass mat started going away inside the ST mufflers & now the car is so loud, it's almost unbearable to drive or ride in.

My suggestion would be to replace with different mufflers & add a pair of GOOD quality glasspack-type mufflers (resonators) that have a body length of 18" at the rears. If you can't find something, I can build you the resonators. 3" dual exhaust is LOUD - there's no two ways about it. Also, you don't really need dual 3" exhaust unless you are over 500 HP, & even at that you can run dual 2.5". I have customers with 800 HP running dual 2.5" & they don't notice loss in HP or flow until they go over 4800 RPM.

Using a real resonator would be far better than glass packs. I used Flowmaster resonator on my 1969 6.1 Hemi Cuda (2.5") and it totally eliminated any drone.
These are the 3" versions https://www.holley.com/products/exhaust/builder_components/resonator/parts/15110
Jim

With a warmed over 360 and stock 2 1/2 inch H pipe on my LRT, my son installed FlowMaster 40's with 2 1/2 mandral bends to go up the stacks. At idle its not so bad but at 2500 RPM I need ear plugs as that drone sounds like a nest of 50 birds are in the cab. Can NOT go on the freeway at 80 MPH as its so bad. Forget opening the slider rear window and rolling the windows down.

While I'm putting my new 410 Stroker Magnum 5.9 in I am going to Magnum SS shorty headers, 2 1/2 inch 14ga SS pipes and SS mandral bends, SS X pipe and Magnflow muffs.

Thanks! Keep it coming👍
For your interest I have ran both engines that have been in the Challenger in a 68 Charger without any drone.
The Charger has 2" TTI headers and 3" TTI x-pipe and Dynamax mufflers. No glass packs.
This system has been used 13 seasons now.

The shorty headers on the Challenger have 2 1/2" collectors dumping into 3" pipes.
The 2" TTIs on the charger have 3 1/2" collectors dumping into 3" pipes .
See where I'm going with this? Pipes bigger than collectors is asking for big time drone.
You either need bigger headers or smaller pipes on the Challenger. Probably both.

Ding!👍😀 Didn't think about that! That might explain why the drone got worse with less displacement, less cam and smaller heads!? Altered exhaust speed and flow going from small to big pipes?
Can you explain a bit more what is going om then?
I want to swap the shorty's for a pair og full lenght headers anyways, so stepping up to 1-7/8 headers might help.
Do you know who offers good and reasonable priced headers and exhaust systems that will work?

Very easy fix!
I had same problem with my Hemi-cuda. Took the 3" magnaflows off and installed Walker VT mufflers, drone is completely gone, a pleasure to drive!
*** lots of guys complain about the door in the muffler banging sound, I have only seen that on cars with No tailpipes. Mine are quiet.