6=8 and bore over?

I have no idea why cylinder 5 is the one that seems to fail. I also have no idea how low-compression and throwing a rod could be related. If anything the opposite should be true (less force).

The early round-top radiators seem prone to split the upper seam, usually on the front side where you must remove the radiator to re-solder it. Happened on both my 69 Dart and 65 Newport. Whenever I re-soldered, it would split again within a year. A radiator shop guy told me that was common. He said he soldered in a copper cross-brace in the top to try to hold it together. I didn't see that, and not sure if a designed solution or something he came up with. The later square-top radiators don't seem to have this problem, but the round-top is sure prettier when painted nice.