[RocktimusPryme]

Originally Posted by Jay S

But overall it appeared the extra stroke and cubes were more important than the bore.

I think thats probably going to hold true in all but extreme examples. As long as you have a reasonable valve size, adding more CI is going to have a larger impact on power, than adding more valve size without adding CI. Of course if you can it would always be better to add both.

When you are CI limited, bigger valve will make more power. Assuming supporting modifications of course. The DZ and Boss 302 from the Trans AM Series come to mind. The Ford motor flat out made more power because its heads had a 2.23 intake valve compared to the Chevy 2.02. They should have won more of those races, but the Ford's couldnt stay on the track. Jokes write themselves. I also think Ive read that a wedge head motor is a more efficient design than a hemispherical chamber, but the HEMI simply allows you to shove larger valves in it, which on the dyno or at the top end of the race track is going to make bigger numbers. Engine masters did something like that with a Hemi and a wedge mopar, where the HEMI would have won a drag race but lost everywhere else.

Im sure if you graphed a static CI engine with different valve sizes and a static valve size with varying CI there would likely be an equilibrium somewhere.