318 head porting for the average joe

cut the valve and seat
works to give more "curtain area' for low lift grinds under .500 roughly
of course really high lift cams can go more than 45 degrees
It's also a way to get a new higher seat just sitting the valve on top of the old "top cut"
which it appears the head in question does not have much of
for the valve you have to start off with a larger one and cut it down or the edge gets too thin
I usually measure the curtain at the inside of the seat
others use the outside