Depends on cc's of both heads for comparison and port air flow of both sets for comparison,the 346's probably have less cc's than the stealths[ combustion chamber]thus more comp, and smaller chambers, thus more velocity than the stealths,in out of the box perf, mil the stealths and play with the timing,change carb jetting, the stealths have alot more potential than the 346's, but the 346's probably outperform the stealths in stock form,I have seen some pretty mean cast iron heads run in the low 10's on 440's....