I have a little experience with this on the flow bench with years of testing that very concept. A couple of years ago, I had a friend who had a set of CJ heads that ran well, but wanted more. He brought me the heads, and they had 2.190 valves installed with 1.710 exhaust valves. I flowed the heads before touching them, and was dumbfounded with how the intake did NOT flow. A well know engine builder had installed the larger valves with 30* seat, but did not do an appropriate valve job, and the flow was down to 230ish cfm. I cleaned up the heads, installed a 2.100" intake valve, and the heads flow 280 cfm now. I have seen all brands of heads do the same thing, only to lose airflow. There is also another down side, and that is the weight of the valve increases, requiring different springs to keep them from bouncing or valve float. My question is: Why install a larger valve if it moves the edge closer to the chamber wall, and cylinder wall and decreases flow? Bigger does not always mean it will flow more. I got the same flow out of the BBM heads with a 2.090 valve as with the 2.200 without any porting. Same with the Survival head. I got 352cfm with porting and 2.150" intake valve. The Edelbrock heads work well with 2.150 intake and 45* seat. I also have always tried to keep the throat diameter at 89-90% for intakes, and 88-90% for exhaust valves. Ultimately the heads work well with anything over 70% bias for the exhaust flow. Divide the exhaust flow by the intake flow. Another thing I have used in the past is to flow the intake tract without the valve, (valve stem installed upside down) and then see how much flow is lost around the valve. If you can get a valve job and port shape to keep the flow to within 5% loss with the valve installed, you have just about optimized the port and valve job and unshrouding. There are many more things to consider in a good valve job than a larger valve. JMO, but it has been my experience. Joe-JDC