Temp is 210 as verified by an additional temp guage. Thermostat was changed to a 160 with no change in engine temp, and now back to the 180 thermostat. Radiator is an aluminum two flue, fully shrouded with a two speed electric fan. Temp gun on the radiator shows 30 degree drop in coolant temp. Water pump was removed inspected and checked and is the correct rotation and moves water as intended. After viewing Elderbrocks PDF on the heads it indicates that early blocks need to have a steam hole drilled at the 1 oclock position to remove air trapped at the intake side of the cylinder. I have redrilled the holes. I also found the engine block to have a large amount of scale/rust that the passage between the cylinder walls where blocked with deposit. I used a long feeler guage to knock out he rust and flused the block of sediment. I'm thinking this may cure my issue but I want to be sure there isnt something else I'm missing.