All engines will respond to prop changes similarly, but what MJD was saying is that trying to get big results one way or the other from an engine that wasn't designed for that purpose can be a waste of time and an unwise use of that particular engine. The engine designers use different timing events and port sizes for the intended rpm range or in a competition engines' case, for its' maximum output. I guarantee that you will get more rpm from any sport engine by changing the porting and the increase will be in effect for all props that this sport engine would normally turn.