[Charlie Brengun]

For me to get my car to pass inspection I cut up the flowmaster system and removed the H pipe piece and welded in a pair of bullet mufflers. That brought the noise level down but for this topic it also removed almost all the drone. I have a pair of aerochamber mufflers on the car and they drone a lot (on my car).

What I am planning to do, as the car is too quiet for my liking with the bullets, is installing flex couplers (like these https://www.ebay.com/itm/143213752138) after the headers and using the original style hangers like FormulaJones suggests.

Hopefully the flex pieces and the hangers will keep the drone down (and give me my sound back)

[Lifetime Goat]

The drone is there with the top up or down. Although with the top down there is a lot of other noise to keep me occupied.

[The Champ]

Originally Posted by Lifetime Goat

I purchased the Pypes H 2.5 in system in 2004 which came with Dynomax Turbo mufflers hooked up to RAIII manifolds. System sounds great above 3000 rpm but when I am just cruising between 1500 and 2500 rpm the sound is awful.
Is this just the way it is and if so are there any good choices to replace these for a quieter sound?

I have a 462 in my '64 GTO Convertible with a 2.5" X pipe system and the long Dynomax Turbo mufflers. Absolutely no drone whatsoever in 9 years of driving it this way.

[Tarl]

Originally Posted by The Champ

I have a 462 in my '64 GTO Convertible with a 2.5" X pipe system and the long Dynomax Turbo mufflers. Absolutely no drone whatsoever in 9 years of driving it this way.

Can confirm. have same setup on my 66 convertible, no drone whatsoever.

[flat-bill]

Is there any relationship between cam duration and/or LSA and drone? Billk

[amcmike]

Originally Posted by flat-bill

Is there any relationship between cam duration and/or LSA and drone? Billk

That's an excellent point. In addition to the exhaust itself, the timing of the pulses and volume of exhaust flow relative to engine speed play a role. Therefore exhaust closing point and overlap need to be considered.


It'd be interesting to hear people's experience with trying different camshaft layouts and whether they noticed a difference in drone without any change to the exhaust system.

[Lifetime Goat]

Epilogue on this thread.
I replaced the Dynomax muffler with Pypes Turbo mufflers and 90% of the annoying resonance is gone. I still get a little at a very specific RPM but all in all I am happy with the result.
Thanks to all those smart and experienced people who commented.