I did a compression test this week on the O-340 while I had the cowl off for other reasons. Two 78s a 77 and a 76.

One thing I did was add a keeper for attaching safety wire to the quick drain on the oil sump. There never was an attach point on the sump (maybe there is now?). This is a simple formed U channel with an .812Ē dia. Hole in the middle. There are two flats on the sump boss and the U touches these and canít rotate.