Hi,

My exhaust is a custom welded job with H pipe and Dynomax Super Turbo mufflers. No drone with Eddy 750, stock heads and intake. Switched to Eddy Performer heads, CH4B intake, and Holley 770 Avenger. It was significant before carb change but even more noticeable after. Now pretty annoying drone at low to mid RPMs. Previously switched from some Hooker chambered mufflers to rid a drone. Any ideas?

Thanks, Pete

Check the ign timing , Vacuum advance?

Odds are when you swapped the heads the exhaust touched somewhere, look closely, everywhere.

Some folks confuse 'drone' with just a loud(er) exhaust noise in certain rpm-ranges.
IMO actual 'droning' is when other nearby parts like sheetmetal or interior parts start to vibrate along with the exhaust and add their own noise to the exhaust.

It's also quite possible ofcourse the new intake and cylinder heads create more cylinder pressure now which increased the exhaust noiselevel a bit.

I also believe the type of exhaust hanger used can also increase interior noises by transfering exhaust vibrations to the body.

Very likely the exhaust is just louder now w/ the added power.

so you are running manifolds? If so, adding resonators in the tailpipes will fix it.

The drone is a resonant frequency that can change with the length of exhaust and other factors. I've had it come and go with a simple change of mufflers, same length, different brand/model. How to get rid of it? Sometimes a muffler change will help, sometimes changing the length of the exhaust(harder to do).

Agreed, adding some "cherrybomb" brand glasspacks alongside the leaf springs will work wonders. they are cheap/louvers are punched outward/they do not neck down where the nipples are welded to the case. I run em on my truck (my only mufflers) & they do work.