Yep thats the insert, I remember reading theres enough material to tap the actual holeVans CB8-31 =Lycoming 65614 Plug, Baffle Attaching?
I need to acquire one of the round threaded plugs that go in each cylinder head, so an AN3 bolt can be used to secure the baffles. It is Lycoming part 65614, available for around $25, plus shipping from many places (Lycoming's list price is $24.57). I'm wondering if Van sells a cheaper...vansairforce.net