If you have to copper coat head gaskets, there is an underlying issue that you are band-aiding.
Proper machine work takes care of things like that.
We can account for proper machine work. The things that we can't account for are manufacturing defects, porous spots, etc. Once you have a couple on the dyno that are pumping water throughout the engine or bleeding
oil internally because of a drill-through, you really don't want to mess with them anymore.
Those kinds of things turn me against aftermarket fe blocks pretty quickly. I've had 2 aluminum blocks that were returned because they failed pressure tests, a cast iron block that needed a sleeve out of the box, and Barry has recently had 2 cast iron blocks that bled out internally, and one that had excessive lifter bore clearance out of the box.
The engine builder usually gets stuck with the repairs since none of us think the customer should have to be involved.