val and val. job??? for the head guys

hay bob the 5/7 angle is the val. job either 5 or 7 just like the 3 angle as what the mach. shop tells me and they said its better due to the angles for more flow but i have no idea...also ive always heard that the new nail heads where better by design and stem that has better flow pot. but i just know what i have been told over the years....had a set of econo w2 that i got new no val. or anything and was told to use them for more perf.