[Gary D]

Hi, First thing I would check is combustion gases/heat getting into your coolant system. I fought a heating problem for a long time and it turned out o be a bad block that had been repaired with a sleeve and I believe that hid the real problem. I bought a rebuilt 455 and had to rebuild it again. A bad Craigslist experience!! Long story short after trying every cooling combo available I finally checked for combustion escaping into my coolant and solved the problem. Destroyed that block as not repairable, transferred all my parts, problem solved. Just a thought!