I have both and dynoed both.
I have a set with Classic Chambered mufflers, and had them dynoed. I was amazed at the power increase I got. With that thinking, and another set of old side pipes from a local buddy that decided to go sideways over his neighbors mailbox(no name mentioned), I decided that if 3" core is good, 3.5" core of a Howe must be better. When I got it dynoed with the Howes, I found out that it will make more noise, but not more power. Not only that, the extra noise is actually fatiguing.
Quality of construction favors the Classic Chambered since it has aluminized steel. Where I work also has alot of acidic fumes which will cause bare steel to oxidize quickly. The aluminized steel has lasted without red rust. The Howes use bare steel with a spray paint on the outer shell only. The Classic Chambered also has expansion joints, which will help with the stress of heat cycling over time, whereas the Howes do not.
The louvers on the Classic Chambered are deeper and allow it to shave off the expanding gas(noise). The Howes are shallower, and as you can see from this picture, are practically useless.
Believe me when I tell you, the Howes sounded great when I first tried them. It didn't take much driving, and a few sour faces, for it to get old quick. Classic Chambered's are loud enough to get you the grins, but not too loud as to be offensive.
I'm glad I tried both though, because now I know. Not that its ended there, because I have another set in the works.
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I have a welding fixture for side pipes, might as well make sure it doesn't get dusty.
R