#4333, "RE: Headers & tower bar" In response to In response to 0
A 4-2-1 header goes from the four pipes bolted to the cylinder head into two pipes and then into one. The 4-1 is from the four pipes bolted to cylinderhead directly into one pipe. The 4-2-1 usually gives a more broad powerband, while the 4-1 is better suited for high-rpm. I may be a little off on how the 420a responds to these two, but that's how my v-8 experience was.