The S7 engine work is temporarily on hold. The crank went to the local NAPA machine shop last week.
I'll be trying to put a new main bearing (probably a new crank) in my Yamaha XS650 and get that cleaned up before I continue with the S7. This will give me some extra time to consider how to place an o-ring in the head gasket to insure a good seal between block and head. My initial thought is to widen the hole in the copper gasket to make room for the o-ring. After that I can countersink the hole in the block until I get the needed crush on the o-ring. More to come on this subject.