With a T-Stat set up 160...I use the Rex T-Stat set up (nice).
PS. also kinda depends on what the engine piston clearances are set up at. Example no stat with tight piston/cylinder wall clearance = cold block and hot expanding pistons= bad.
I also noticed my engine ran better when the water temp was up (160-170) vs without a t-stat and the water temps fluctuating between 110-170...this was when I tryed to control the water temp with the gate valve at the pump, not a great idea.