CS, very good questions. With them constructed from all st. st. parts, corrosion is not as big of worry to me. They are cheap enough right now that I could live with the worry of the spring eventually fatiguing. I think it is 302 or one of the spring alloys of st. st. so it likely is long lived as well.

Seriously though, we just put a set of 17956's on a 12 second 68 360 barracuda. I have two more with the weaker spring (17156) coming this week and we will do a comparison between them to see what affect the spring rate has on back pressure and sound level at various RPMs. It is weird that such a short muffler, with a 3" core with minimal packing, has such little resonation and roar.

I have had 340s since 1978 and they are very tough to keep from resonating from 1800 to 2300 RPM. This muffler seams to prevent that roar very nicely.

As soon as we get the whole system sealed and leak free, I will try to get some very good sound recordings to share along with the data we plan to collect. Should get measurements later this week.

Tom Hand