[wilkin250r]

I'll be 100% honest, I don't have much experience with chevy motors, but I DO know engines in general (lots of motorcycle performance), so I can tell you the basic theory.

Smaller exhaust means the gasses have to move faster. This is both good and bad. Air is not weightless, it has mass. And thus, when moving, it has momentum. The greater the velocity, the greater the momentum. That momentum can actually be used to do work, to help create power.

I won't get TOO in depth with cam profiles, overlap, and scavenging. The important thing to know is that exhaust velocity is good, and smaller pipes have better velocity at lower RPMs, but they are restrictive at higher RPMs. So smaller pipes are good for low-RPM performance and torque, larger pipes are better for higher RPMs and maximum horsepower.

However, terms like "smaller" and "larger" are all relative to engine size. 2" would be huge on a VW bug, but would be tiny on a 454.