Loose valve guide in block

[swedishsteel]

What do the experts do to when an exhaust valve guide is loose in the block???. Situation: bought an 8n Ford tractor (same valve guides as flathead). Sat over winter and front three exhaust valves stuck open. #3 guide loose in the block so it was able to drop down and ride the lifter with the spring compressed. No damage done. Got everything apart and rust cleaned away on valve stems and inside guides. There is a lot of oily carbon in the valve pockets on that cylinder, but the top of the piston has no carbon at all on it--indicates oil coming up that valve guide to me. My first choice would be an intake guide rubber seal, but I don't have one. Ideas and suggestions welcome. Rod