I just pretty much lost my own sale on some really clean, ready to bolt on 516 heads. I explained fully to the potential buyer the differences in them VS say a 906 head, the exhaust valve difference, no hardened seats, the intake port floor......all that. I shot myself in the foot, because he decided they were not what he wanted. I couldda talked them up and probably sold them because he was genuinely interested. But that kinda thing aint in me to do. ........and we could REALLY use the money right now. I cannot justify trying to make something look better than what it is just to make a buck. That's not who I am. Can 516s be made to flow? Hell yeah. When I get done with mine, they'll support 600 HP. But I'll have a lot of money in them. BUT, I can put that in them a little at a time, so that works for me. I'm just real particular that when I sell somethin, there's no miscommunication and the buyer knows everything I do about the item.