you can mod up a V6 or I4 as much as you want, it may be as loud as a V8 big block but it won't have the same sound.. its not just going to happen, the firing sequence is what gives the V8 its characteristic sound.
ever heard a Viper up close? sounds almost honda-like. a Lambo winding up to high rpms will sing for you, but it ain't no loping grumble V8