I learned how to do valve jobs in my high school auto class but that was just basic valve jobs. Then I learned alot more of the porting and all on my own as my brother bought his own valve grinding tools when he had his own shop. I also found out you always spend way more time porting heads then you think you will spend. These 906 heads here I did my own porting on and I installed the 2.14 and 1.81 valves myself with my brothers machine shop valve grinding tools. We had the tools to cut the guides down for the smaller seals when going to dual springs and even had the tools to knurl valve guides. These are the 906's I used on the mild 440 I had in my 63 for a few years. I opened them up and put the 2.14 and 1.81 valves in them and then worked and blended the bowls along with the rest of the porting. I know I spent at least 40 hrs in the heads and I found out that after I had back surgery there was no way I could port heads any more. Just trying to bend over the heads for a few minutes was impossible with my back problems. This was the last set I ever ported as it was right before I fell and had back surgery. I never flowed them as we had no bench. I just did them as I had learned over the years but I was by no means a profesional head porter. I did many stock valve jobs over the years on friends and customers cars but most were just stock daily drivers. Just mine and my hot rod buddies were the ones I ported myself. I enjoyed doing it but never flowed any to know how good they were. I only knew what worked when I put the heads back on the cars and they went faster. So when I bought my EZ heads I had Dwayne Porter do some of his magic on them. He is a pro and there is no way I could be anywhere as good as him as he has done thousands more heads then me and flows them so he knows what works. I always enjoyed the pride of building my own engines and doing all the work myself but I was a profesioal auto repair tech for my living with my porting and hot rod skills as my hobby. I cant thank Dwayne porter enough for the great job he did on my EZ heads for me. He is a profesional head porter and knows just where to port and what works the best. Here is a pic of the 906's I put the 2.14 and 1.81 valves in and used on my mild 440. Ron