DIY exhaust resonance cancellation

[Mike C]

Glad the Noico worked for you. I was very happy with the product and pricing compared to most of the other choices.

[dagnabbitt]

I have installed my new 355 in a 1981 Chevrolet SWB, very happy with the engine itself but the new exhaust that has been installed has a consistent and very loud drone that occurs at 2000RPM, and again around 2500RPM. This drone has made the truck more or less undriveable. The muffler shop cannot figure it out, they have tried as of today four different brand name mufflers and cannot eliminate the issue.

Truck has brand new stainless exhaust coming off of 2.5 inch ram horns manifolds, going through a crossover and into dual mufflers (four different ones so far, like I said) then goes over rear axle and dumps at 45 degree angle. Dumps do not seem to be the issue since it drones even up in the air on the hoist.

Going to try the J pipe route, looking at that spreadsheet now.

[AcampoDave]

Good to see my old thread back from the archives. Post an update when you get those j-pipes done. It seems resonance is a common problem and alway seems to come it at the speed/rpm we most commonly drive. I did pretty much get mine killed....finally.

[AcampoDave]

Originally Posted by AcampoDave

I figured I'd give this one another update since I've done some more stuff in the name of peace and quiet.
First, thanks goes out to MikeC for the recommendation of the Noico. I went ahead and did the floor, and back wall with the Noico Red version and it's a great product. I also found that my mainfolds really didn't seal too well to the block. Not so bad as to say "Hey dude there's a leak here!" but bad enough to be noticeably quieter after having them resurfaced at the machine shop. I also added a crossover pipe, which does soften the tone, as well as second resonator to each pipe right at the end. This one also made by Vibrant. It's a sweet little stainless bottle style job that really helps.

Another update: I removed the bottle resonators and put them on my mostly stock truck with stock type (restrictive) mufflers. In their place I installed another pair of the Ultra Quiets for a final combo of Ultra Quiets fore and aft of my Super Turbo mufflers. I don't hear the exhaust much anymore at all. I guess I made a great exhaust for a "sleeper".....now if I only had another 100 cubic inches under the hood.