AFR Heads

I have a friend and was helping him out with his small block chevy, the heads are AFR, and were ported many years ago, he thought they would flow over 300cfm, i flowed them on my bench at 260cfm, and when i told him, he thought i was crazy, put the car together its 350ci in a Nova, and it runs 9.80s, and i am sure he thought they flowed big numbers, he pulls the heads for a freshin, has them flowed buy someone else, and they go 265cfm, so i agree, big flow do not always mean fast ETs. or big HP.