OK, This is the tool that has always worked for me. Note the notch at the small end of the tool, that goes into a groove at the small end of the guide. At the top the part that gives the valve head room to come up is on a swivel. Once the large horseshoe clip that holds the guide in the block is removed this tool forces the guide, spring and valve out as a unit. I have only had to put a cheater bar on the handle once but it has always worked.
Picture is also in my MISC album.
I just looked and there are several of these K&D 918 valve guide tools on Ebay now.