DIY exhaust resonance cancellation

[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.

[The Rocknrod]

I don't have an exhaust yet so I've been watching this. So a cross-over pipe and resonators are they key?

[AcampoDave]

Originally Posted by The Rocknrod

I don't have an exhaust yet so I've been watching this. So a cross-over pipe and resonators are they key?

Yes, but I've learned more than that too. See the thing is as you get it quieter you hear more noises that you never noticed before. As the exhaust note diminished I noticed lots of noise from the motor. That led me to switch from an air filter housing that was open 360 degrees to one only open in the front. (kind of my homemade version of the old Caddy unit.) That helped by dulling the sucking noise of the carb. I also learned that even a small hole in the firewall like a deteriorating grommet was a conduit for noise. Dropping a light under the hood and looking cabside in the dark suprised me at how many litlle gaps around hoses and grommets needed to be addressed. Also as I mentioned above, the manifold to block seal. I never hear a rythmic click or anything from there, but turns out it was an overall dull roar....and the stink of exhaust when working on the motor while it ran. After machining the manifolds I was able to lose the gaskets and when I fired it up I was surprised that what i thought was normal motor noise from the carb, fan and belts was actually the dull roar of leaking exhaust! Then I said....."Hey, I think my alternator is getting loud"

[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.