Alright: nobody has asked: Did you give the system a good flush? I mean using the two part caustic, but first pull the block petcock and rod inside best you can, then replace with a ball valve and hose plumbing for garden hose. You will need to flush from here and drain out the top of the radiator. You can get one of those plastic setups for that. Get that solution in there, and bring it up to temperature. Let it work. You will find all kinds of leaks. Water pump packing will probably fail. But you will be getting rid of the crap that prevents heat transfer. Just my two cents. I did this with my '49 216, and the stuff that came out was disgusting....
