Hi Bruce,
Sometimes valves need to get used to your hand. If the way you hold the instrument is different than the previous player, wear patterns might be different. However, my experience with bottom sprung Conn valves of the type on your 80A is that provided the corks and felts are good and everything is clean you might benefit a from a new valve guide. This is the round cap that fits under the top valve cap and has the rod sticking down into the valve. If just one of your valves is problematic (often the 3rd, for me at least), you could try switching the valve guide with a valve that is OK and see if the problem follows the valve guide. New valve guides apparently can be found. I gather they are in the Allied catalog. Osmun music should be able to get them, if they knew what to order. I should hopefully be finding out in the not too distant future what the article number is.
Here are two articles on my website about the style of valves in your 80A. The bottom and top valve caps are different, but the rest should be the same:
http://www.xs4all.nl/~cderksen/ConnArticle36.html http://www.xs4all.nl/~cderksen/ConnArticle37.html
I am planning on writing something on sticking valves and these valve guides.
As for the 80A:
http://www.xs4all.nl/~cderksen/Conn8...1956image.html
The picture is for a 1956 model, but other than different valve caps it is identical to your 1968. The style valve caps you have were introduced in 1958.
Regards, Christine