Couple months ago my fairly new 331 started to over heat at 215 degrees or so. I discovered that there was parts of a rag stuck in the t-stat area. I pulled it apart and replaced the t-stat and flushed out the engine with a garden hose for approx 20 minutes. engine would only heat up to 150 or so and still that took forever. I verified that my new guages inside the car were right with an IR gun. The rad was clean and full of coolant right to the top. Still didn't work so I pulled the water pump off and everything looked fine with the inpellers and what not. Still didn't work. Top of the rad was cold/warm at best... same as hoses, So i had my rad rotted out and core rebuilt. Now its a little better it comes up to 160 but still takes a long time but atleast the top of the rad is much hotter than it used to be. Bottom of the rad is still fairly cold though. I have tried 3 t-stats aswell. Engine use to always run at 190 or so and the temp came up fairly quickly but not no more. Engine will run like crap for awhile cause its so cold and will not warm up. Its a real PITA. Anymore ideas. Maybe take it to a rad shop and have them pressure test it? Seems pointless though if everything is allready new. Thanks.