UPDATE 2005-09-25, About the expansion chamber
As I mentioned earlier, I got hold of an old Sport -exhaust system.
I know that new ones are availlable from the Swedish Saab Club, but
I wanted to see how they are made. And perhaps make one for myself.
Outwards the standard and sport exhausts look pretty much the same, but the sport version has double exhaust pipes (above).
This is a blueprint that shows the inner structures, klick it to see
it bigger.
The casing has two layers. An outer layer of sheet metal and an inner layer of perforated sheet metal. Sandwitched between those, is a thin layer of glass wool, serving as the muffler material.
The double exhaust pipes and the perforated tube.
A different view.
Tip of the expansion chamber has hole of about 20mm diameter.
The diffuser cone takes up over half of the space inside.
The starting point of the diffuser (pic above) is also perforated and
the space between it and the inlet end of the muffler is filled with
glass wool (pic below).
More
shots of the structure:
The attachment iron that secures the expansion chamber to the engine
block.
The curved part is made of so thick material, that one could propably
still use it.
Here's what the Chilton manual says about modifying the exhaust system for more power:
Click the image to see it bigger.