Well, I think I have found the source of our elusive overheating problem. Now to recap, the engine was flushed multiple times had all compoments replaced and rechecked and still when running at 45MPH or higher the engine temp would climb to 220+. All check came out OK no compression leaks or other leaks so what could it have been??? Take a look
Look what I found when I removed the freeze plugs.These are up to 1/8" thick (to big to pass through the cooling ports in the head or block, but plenty big enough to stop circulation around the heads or to block a passage under high waterpump pressure. These appear to be casting flashing that rusted and and finally broke loose. Caused by running the block with water only back in the 60's.
I will know for sure this weekend when the engine is back in the car.
Take care,
Mike