I have been having an issue with oil passing into the coolant system for some time. The shop that prepped the block did the oil passage modification.
The radiused adapter area, galley plugs, offset crank oiling orifices, oil pump at block. The two galleries were drilled to 7/16" at the oil filter adapter.
Do either one of those passages intersect or parallel to a water jacket with proximity close enough to have been compromised?