912 engine question
 

Im taking the heads off my 1965 912 I found only valve stem seals on intake valves & none on the exhaust valves ? could they have burnt off ?

I think it may be possible if your valve guides are so worn. What do the valve stems look like?
Was this engine smoking ?

Most engine builders that I know of don't bother with valve seals on the exhaust valves. Some believe that you should leave them off the intake valves too (der Maestro being among that crowd) for better lubrication and longer valve guide life. Others recognize that the oil leaking into the combustion chamber past the guides when the choice is sans intake valve seals, will cause detonation. My views is skip the seals on the exhaust valves, use 'em on the intake valves.