440 overheats once and then it's happy all day

I would use one of these stats by Robert Shaw/Flowcooler. They flow much better and open smoothly. This one is 160 but they are available in 180 I'm sure(check Mancini?). Just a thought. I've had my share of issues with Stant caps and stats even on daily driver cars.

http://www.summitracing.com/parts/bra-330-160?seid=srese1&gclid=CJXnj9y32b0CFYsWMgodfEUAEg