Thanks for the response Sam, Keith, and Bill.
Yep, Dad's wagon really flies and is amazing to drive. 11.50s at 115 through 2.5" mufflers with a 3.31 gear, iron intake, a Q-jet, shifting all by itself; it is like driving a big Cadillac on the strip and rides darn near as nice since it is so heavy.
I can tell you from speaking to the inventor and looking at the patent that there was probably no performance improvement when using these in the open mode and if there was, it was not measurable on a stock engine. These are so restrictive even when in the loud mode. But the sound definitely changed drastically. However, we made changes that make differences but we have not drag tested or air flow tested any. I think we can make even more changes and help more but it would be impossible to ever make anything as good as the Walker UltraFlo, MagnaFlow or Goerlich's Xlerator. Straight through is hard to beat!
The mufflers are very expensive to build. They are all 304 and 409 st. st. and they have a custom actuator; the parts alone cost me more than most st. st mufflers do.
It is about four hours of welding and fabricating labor for each.
Bill, I do not have source. I did not set out to try to duplicate the option, just have fun creating the mufflers
. We do use a pneumatic switch to actuate them and you are right in thinking that it does not look as cool as stock does.
The mufflers I have down the basement now are 2.5" in and out, offset-offset. I have enough prepaid parts to build six pair (that are spoken for). If we get good at it and can cut down the time it takes, I suspect we can build some more. Time will tell
Tom