I was installing my new BB valve springs and I noticed that some of the valves, especially the exhaust, did not move up and down as freely as some of the others. One exhaust valve was very difficult to remove.I purchased these heads (215's) about 5 years ago with supposedly less than 200 miles on a rebuild. Shouldn't I be able to remove a valve without a lot of effort?

I suggest using some penetrating oil to try to loosen them up. Be sure to lube them generously when you put them back. They should slide freely. Looks for any rust on the stems. Check for mushrooming at the stem tips. Bent stems would make moving them difficult, too.

Tino,
Have you been running the heads, or have they been sitting ? If they have just been sitting, you probably should at least do what Pat said. Personally I would take each valve out, clean out the guide with a brosh and some brake kleen or other solvent, then reassemble the valve with some EOS or other assembly lube on the stem. If cleaning the guide and valve stem does not free it up, you need to get them to a machine shop and find out why, or face the chance of a stuck valve when you start the engine. The other possibility is, if the valve is loose but just wont come out of the guide, it could be burred up some at the keeper groove. Take a fine sharpening stone and run it around the groove lightly before pulling the valve out.