318: too much cylinder head?

To much porting/ over sized valves on a street motor will cause a lag in the bottom. The heads I have are hogged out, with larger valves (cast iron). A friend that has been racing Mopars his whole life said they as good as very worked X-heads, I was going to put them on a 273 , he said no. Yes , I am off topic. However, if you have the right cam, gears, ect, a properly built mill, will pull hard, throughout the power band/ RPM range.