Valves here we go again! But...
 

Please see my thread in tech section if you can help I can't work out how to transfer it here but maybe it will help others .
Not a typical post but I'm sure some of you here have experience

Link to the OP's original thread:
http://www.peachparts.com/shopforum/tech-help/395319-om617-valves-again-yawn-but.html

If all the valves were tight, it's worth rechecking the clearance. If they're tight again, readjust and continue driving, checking, adjusting until they stay in spec. 260PSI compression is poor. If the valves are still tight, they'll affect your compression results.