exhaust drone/harmonic resonance

I know that an H or X pipe is supposed to cure this exact issue, but I'm starting to think it's the cause. I've never had a drone like this before, but I've also never had an H-pipe before. Has anybody tried blocking their crossover pipe to see if it changes/cures the drone?[/QUOTE]


No X or H here, but I have a mandrel bent 2 1/2" exhaust with stock manifolds on a stock 69 340 automatic and the repop 2 1/2" tips.

First set of mufflers were the Summit turbo mufflers. Bad drone at 1800 - 2200 rpm. I swapped in the Dynomax Super Turbos and they sound almost exactly the same. Most people will not be able to tell the difference. Still has the drone at 1800 - 2200 rpm!

Anyone want to buy these Dynomax mufflers, they are for sale.