Both Tango and Denny are good. I ported my 305 heads(first time I did it) and just spent 9hrs. doing it with a hand held grinder. Showed it to a mechanic friend of mine who does it for a living and he suggested I take it down a little more but otherwide he said not bad. He said with the cam I had in my 305, the engine would breathe a hell of alot better. If I really had taken my time, I could have done alot better job after looking at some porting jobs done by my friend. I picked up alot on the higher end after 5,00 rpm's.