This may sound stupid , but make sure you don't have a air pocket in there.. My friends small block was running 210+ , water was running thru the radiator pretty fast. I thought maybe it wasn't cooling down fast enough, so I put a 195 stat in . That didn't help , tried no thermo-stat , that didn't work either. fresh engine with a 26" radiator and big electric fan..
Anyway some how we got the engine to burp , then added water and started running at 195 ..
Weird, but everything is great...We did change the stat to a 180 and now runs about 182 -185..perfect.....