JB weld, flex seal or full rebuild ?

Agreed, and according to UEM/Icon, the 2618 has a higher rate of expansion, requiring more clearance. I had managed to transpose that in memory somewhere along the way. Their site has a chart showing allowable clearance of .035 to .070 for a three and a half inch to a four and one tenth inch bore, depending on exact usage, and a ring gap size to bore factor. Of course there is a lengthy disclaimer about needing to give careful consideration to what the individual demand of the application before deciding where to set final clearances. To me, that reads as a "between the lines" suggestion to set pistons and ring gap more on the loose side of spec than the tight side.