@alextstone posted a thread showing his exhaust valve failure. I also attached an article from Mike Busch. In the article he says you should be able to identify a failure 100 to 200 hours before it happens. I didn't want to add all this to his but felt like others would like to see it.  https://www.savvyaviation.com/wp-content/uploads/articles_eaa/EAA_2010-08_exhaust-valve-failures.pdf I scope at every oil change and while I'm there I do a compression check and rotate my spark plugs. I