Exhaust diameters

[70spider]

Hey, I thought about getting a header for my rebuild but could not find an Abarth for my 1438 motor. So, I was looking at some headers a couple of our vendors sell and it seems the collector is 21/4" in diameter. Is this to large for a 1438 putting out around 100hp. I could get a reducer to go from 21/4" to 2" at the beginning of the downpipe and run a 2" system, would that work?