[alanwoodieman]

remove thermostat, drain any antifreeze/water out of running engine, then put plain cheap white vinegar in the engine, run it thru several heat/cool cyles and then flush it out, I had a 41 plymouth that took two vinegar rinses to get it clean, but every on I have done this too has run considerably cooler after. Use fifty/fifty mixture and put a bottle of water wetter in there and lets go for a cruise!!