Converting a stock manifold to a split system and retaining the original heat riser is by far the most effective way to get dual exhausts that work- - - -sort of. It doesn't really improve performance, unless rattling windows a block away with harmonics is considered to be an "improvement"- - - - -but you'll create fewer problems that way. The trick is finding an old geezer welder who is good at welding cast iron. They're pretty scarce these days!
Jerry
I have to say the stock manifold posted earlier really does look nice. My current single exhaust manifold works well with the "flapper". My performance is fine and I'm not looking for a performance gain but I do like the dual exhaust sound.
