O rings on center case studs on O360?

I am getting ready to join the case halves of my O360 A2F and my old Lycoming book says not to use o rings on the center studs if they are doweled, this is what I will do unless told to do otherwise. The thing that makes me question is that there is a machined recess on one half that would fit an o ring, it would need to be slightly stretched to go around the dowel but it seams like it would make a good seal.

I can't really answer, but know that I would call Divco or whoever worked on your case to get their input. They wouldn't likely put a recess around the dowel, if on oring wasn't used.

Larry

Use O-rings

They are not the same as the standard o-rings used on the throughbolts. If memory serves you need
STD-2013 o rings. I’ll confirm the number when I get to the Hangar latter.
Part # confirmed.