Flathead valves

So I apologize in advance for my lack of knowledge. I pulled the heads off of my 51 Ford. One of the valves had what I am guessing to be a seal loose and hanging under the valve like a ring. I managed to tap it back into the block. I am guessing the valve was stuck and the seal popped out when I started it. It had not run since 1990. Will it be okay or do I need to replace it?

 

do you have a pic? it almost sounds like you are describing a valve seat

 

Yes, sorry. I believe it is the seat. It is a ring directly under the valve.

 

ya that is the valve seat.you might want to peen the bolck in four places around the seat or their is a good chance it will pop out again and also check the face of the valve for any irregularities

 

Clean and inspect area VERY carefully...loose seat is often caused by a crack, usually the dreaded valve-to-bore crack.
If block is good, Joblot may still have some of the slightly oversize dry-ice fit repair seats. And peen for good measure. Valve may be junk from its seat hitting against the loose block seat...