tony they look like the best in flow# across the board from .300 to 600 lift but only come in 58cc chambers not sure where my comp will be with these heads, think ill have to take my motor to my engine builder and see what he can come up with as i dont want to quess on that, mainly i just want a 500 plus hp motor for once in my life seems like i never get my combo right with the last 2 people i used, when this motor was done last yr i took all these parts and motor to my engine guy and he said i should have went with alum heads along with a bigger cam but said this will be ok for 465 475 hp not bad but we all want more power down the road as long as its streetable thats where it gets crazy, i dont want a motor that sucks in traffic and starts to over heat it gets real hot here in nj in the summer, either i buy new heads along with cam or port my roush heads and maybe custom cam and port match the vic jr manifold??.