Ok fine...but where's the quantifiable proof much you loose in an application like this? Engineering calcs? Dyno tests? Science it out for me if you're so worried about it.
Considering the old MM build where they used stock x heads with a good valve job, headers, comp xe 268, air gap, and a 750 edelbrock and got 391hp...with the heavy *** pistons. You guys make it sound like the difference would be 25-50hp in 400hp...when in reality I'm sure its well below that...probably closer to 5hp at high rpm.