How about a comparison before and after blocking the intake manifold exhaust crossover. Some have said there is an audible difference.
Engine is 1971 455 overbored to 462, 6X-8 heads running about 9.75:1 CR, Comp Cams Magnum 280, 800 cfm AVS e-brock carb on a P4B. Exhaust is Hooker Competition Headers, 1.625" x 28" into 3" collector, 2-1/4 inch exhaust pipes back to Dynomax Super Turbos, no H-pipe, no X-pipe.
First link is the way it sounded before I blocked the intake manifold exhaust crossover:
http://www.youtube.com/watch?v=Fmccth_JWeQ
The second is the same but with the intake manifold exhaust crossover blocked:
http://www.youtube.com/watch?v=Pd3Dm...eature=related
Not sure if I can hear any difference.