This narrative is from Beechcraft owner Elliott S., who documented via his digital engine monitor data downloads the indications of impending exhaust valve failure in his TCM equipped Bonanza.

Data download graphing credit to EGView^TM:

1. April 9:  no one would pay too much attention to this data download.

2. June 5: Is this just a little crud on the exhaust seat of EGT #2 (red)?

3. July 28:  No, I don't think so, but the excursions aren't that big yet.

4. August 7:  Would have done something if I had downloaded this flight.

5. August 21 before cylinder change.  This is what a full flight looks like before the repair - escaped eating an exhaust valve!

Here's another engine monitor save pirep from A33 owner John P.:

"My JPI saved my bacon as well! My indications were LOW (-300deg) EGT on #3 at idle on deck with normal temps during the run-up. At altitude in cruise #3 EGT would jump up 50deg, caught my attention since I was in the "normalized" mode, for about ten or so seconds, then it would go back down to the exact temp as before. This cycle was happening every 5-10 minutes of the flight. Got on deck...compression test....20/80!! Now I have six new jugs and one smooth running engine!!"

To me, the morale of this story is that modern digital engine monitors are extremely useful tools in operating and troubleshooting our engines.

Instead of the big surprise of Elliott's engine eating a valve at a very inopportune time, Elliot was able to make a safe cylinder maintenance intervention on HIS terms.

Elliott's full web narrative can be seen HERE

See more on TCM Exhaust Valves HERE

Be a CSOB (avert big expensive things breaking and causing more financial havoc or a foreseeable engine problem) and put one in your airplane