I had to install 2.20 and 1.88 valves due to the seats and the heads prior useage. 20.00 swpa meet heads that had been running 2.18 and 1.81...I did some valve unshrouding clean up. Not excessive as I need to keep chambers as small as possible. I agree that you can outflow 2.20 1.88 valves with 2.14 and 1.81...the size becomes a factor and gets in the way of flow. Thanks.