The problem was usually the heads, not the blocks. They cracked between the valves. When our shop forman had one come in he asked “How is the heater working?” The common answer was “not so well”. He’d then tell the owner the heads were cracked and we can’t do anything with them.
I wonder why not? True enough that location is challenging.
But, many are repaired in other critters. Why not RR? I have no ide if the R%R heads are alloy or iron.
But, perhaps, mere patching is below the dignity of an RR and certainly, it’s owner.