Hey, Tony, you're good!
DA-20-C1 w/ Cont. IO-240
Yes, hole in the cylinder casting. Odd thing is a chunk of aluminum was lodged in the lower spark plug. Appeared to have been bounced around quite a bit before it was captured. Mechanic thinks it's possibly a void in the casting that failed thru-wall in both directions.
Found during compression check. The reading was in the high 60's. It was the hissing sound that give it away.
The plane is just over 3 years old, but is used as a trainer.
Update: Aircraft was undergoing 50 hr inspection (per Diamond program). Engine had approximately 1000 hrs. Waiting to see what Continental/FAA/Diamond want to do. FAA flew down today to take a look.