390 vs 408

Just for kicks I was playing with areas of circles and assuming a lot it looks like about 8% more area is shrouded witht he 3.91 vs the 4.04 (340) bore using the 2.02 valve. I would think by getting less generalized that percentage will go up rather than down but that's just a guess. You could clearnace or notch the bore... but really, you are minimizing the shrouding. Not stopping it. The only way to stop it is to keep the walls away from the flow path IE hemis.