Exhaust Drone!
 

I have Headman headers to 2 1/2" pipes with X where Cat used to be with Dynomax mufflers. My engine is mildly built with a 515 lift cam.
At idle it sounds nice but at around 1500-2000 rpm the drone is bad. Upwards in the rpm range it gets better. I know this has beem discussed in depth but I tried a search and the topic really cluttered. any info or ideas would be great. Happy holidays!!

It's the Dynomax mufflers. I had a Dynomax cat back with a Cat delete pipe on my mostly stock L98. I had stupid amounts of drone. It was louder inside the car then it was outside. I swapped out the Dynomax cat back for a Flowmaster set up and it was 1000% better. Now the Flowmasters are not perfect either but the car is a lot more enjoyable to drive and it is louder outside of the car then inside.

Add cats, change the mufflers or both.

I just changed the mufflers and was much happier. With the headers it will be louder then mine. Adding high flow cats would tone it done some more if needed without hurting your performance. I would start with changing the mufflers and see how it sounds.

Recently ordered installed then removed the Borla catbacks for same reason, drone! It reminded me of riding around with open headers except less decibels but same super resonance. My wife hated it. I kinda' like it and might put it back on. I know is kinda' false advertising though no horsepower to back up all that sound. some day Melrose smooth flows.

Bite the bullet. Get a CORSA cat back system, let your conscience and applicable laws decide whether or not to reinstall the catalytic converter(s).

careful when recommending Flowmaster mufflers; they come in a short 2 chamber style and a longer 3 chamber style; I've had the "shorties" on two cars and they are a terrible muffler and I would never use one again except where space limitations precluded using anything else.

FWIW, my car has LT headers, cats, and X-pipe instead of the stock resonator, and then Corsas at the back. It still has bit of a drone from about 1700-2000rpm, although it isn't anything close to unbearable/terrible. But this is just to say that Corsas are not a guarantee of no drone at all.

You ruined it with the x-pipe.

Well, technically the previous owner did. OTOH, if you hear it wail in its power band, you might assess it differently. It does sound spectacular, and I got lots of compliments on the music it makes. So it's a tradeoff.

More pertinent to this thread, the OP's car also has an X-pipe, so my experience may be especially helpful to him.

I'll suggest a different solution than others. When I put a chambered exhaust system on my '71 LS5 the drone was absolutely the worst I've ever heard. My kids wanted to use ear plugs when I took them for a ride. I dynamated the entire interior floor and halfway up the sides of the rear compartment. The I took some radiant barrier/foil insulation, cut pieces for the rear compartment and installed over the dynamat. This took 90% of the drone away without changing the exhaust.

My conscience kinda died but I installed a single cat because I wanted to kill some of the noise from the LT headers and Borla Stinger system. It made the car somewhat irritating to the wife as opposed to "I don't want to sit in that car". I am looking at the Corsa system to see if someone has a take off or used one.

I had drone issues on my non-C4 '69 at 1500 RPM with several exhaust configurations. Flowmasters were the worst. After 12 miles of driving with the Flowmasters I threw them away. I still had some drone with the new Dynomax mufflers, but it was at least tolerable. I took Vizard's advice (from one of his books) and put an H pipe right at the header exits/reducers. This got rid of about 90% of the drone, and the car is now quite pleasant to drive.

I have TPIS headers that Y into the cat. Any suggestions?

you could try blocking one exit on each muffler, I did that on my last exhaust and the OBX I have now. you could try just shoving some steel wool in there just to try to see if it works then if you decide you like it plug it permanently.

Buy a pair of Walker Quiet Flow mufflers they will fix your drone problem.They are pretty reasonable price wise also.

Thanks for All replies and info. I have also noticed my muffler tips are about two inched back under the rear valance. I would think moving mufflers back and behind the car would help also. I would love to get a pair of Corsa mufflers but I dont think you can just buy mufflers. the rest of my exhaust is fairly new. I tried to use older mufflers when I had the exhaust done. Now I need to address this. Merry Christmas.

This is correct.

Franklin, you are wanting a bit of both ends of the spectrum; high performance low restriction that yeilds big power and throaty sound.... but with no drone. (corsa fans jump in here and smack me)

You have to have a strategy and then go for balance and your definition of balance.

Of all the countless threads on this subject the only consistent "Zero Drone" solutions come from choice of THE MUFFLERS and not combinations of the headers, cross over, X pipes etc. 2.5 vs 3 inch pipes.

So, for zero/lo drone your choice is either Corsa Mufflers or a OEM/Walker solution. Frankly it dosen't matter what you do upstream.

I had often thought the drone or at least part of it comes from the rear window cargo area floor combination. Anyone with a vert and top down care to comment?

I had same issue with Hedman headers duals and Hooker Aero's. Drone was 75% less with a U shaped crossover abou t12 inch after collector. Still loud but no headaches.