I joined the Jef this week. Had an exhaust valve fail halfway on downwind with a student in the plane. Shut the engine off immediately and did an uneventful glide approach to the departure runway. We also had a low time pilot have the exact same failure two days before. He didn't shut down straight away and kept the engine going which eventually ended in complete engine failure with a destroyed piston, head and rod on number 2 cylinder.
So 2 exhaust valve failures in 3 days. On the first engine it had all the new mods and had done about 500 hours and on mine it had done about 900 hours.
It's all well and good to be trained to always fly with somewhere to land but until you experience an engine failure it's all just theory. I now religiously fly from paddock to paddock!
Last thing, I was on the last of three circuits before I was going to send the student solo! So if the engine had of held on for another couple of minutes he would likely have had an engine failure on takeoff, sobering for us instructors.