Mine don't hit 210. He must have air in his system to get those spikes. Most guys with the inline and 180 stat sit right around 183 from what I've heard. I still don't have a front driveshaft, so I haven't been able to read mine yet.

 

I've been an exclusive AB buyer up until today. I ordered their 180f soft spring only to realize just now that its a Motorad. They don't sell the OEM 180. so I went to roversnorth and ordered the OEM grey 180. I'm liking roversnorth more and more.

 

I believe you are very close to figuring out the lowest ok temp for air/fuel mixture being at correct mix, you also mentioned closed loop kicked in at around 119f , which is reasonable , because it's the temp of a cold sitting engine in a very hot day,, because when we start a car from cold in a hot day , let's say +90*f ,, it only takes it 10-20 seconds for it to start running very normal, because it's coolant is already 90*f to begin with,, after my original post in beginning of this tread , I did a little bit of more digging into older treads & I found a tread ( I believe from 2011,or 2012 ), that a member had installed a inline system with 160* thermostat, & his running temp's were between 165 to 172* or similar,,
& everyone was telling him it's too cold & he will damage cats for running too rich of fuel mixture, it's a long tread & he mentioned he took a long trip & measured his mpg to make sure not burning too much fuel & his fuel consumption stayed around 17mpg as he always used to get,, so obviously his mpg didn't drop,,,, As Cat's go, I don't think if an engine is running even at 150* temp exhaust gases will be any cooler than normal, when combustion is happening in correct mixture, it will produce same amount of heat & burned gasses will be same temp, & has nothing to do with coolant temp (as long as fuel mixture is correct),,
What I am more concerned about is correct oil temperature, & getting it there fast enough,,,, engine oil is designed to performs best at 230*f temps (that's where it's viscosity is measured) so ,, if it drops below 200*f then it is not the viscosity we read on the bottle, it's thicker & will not flow the way it should, if it gets to higher temps, it starts to break down (most oils thermal breakdown is anywhere from 255* to 290*f),, most engines won't get their oils that hot unless racing & constant high rpm conditions,, so we don't need to worry about that too much),, unless we race our discoe's or we overheat them due to cooling problems,,,,
But colder oil will contribute to poor oil circulation , lubrication & will not get rid of moisture that is being produced specially during cold starts & later during normal operation, (almost every engine produces water as it runs & you see it very clearly when it's cold as water dripping from exhaust, each gallon of fuel burned produces aprox a gallon of water,, some of that water produced in combustin chamber gets mixed with oil & finds its way into crankcase, that's another reason why oil needs to get to 230*f, to evaporate water as quickly as possible, short drives are enemy of engines, because of lack of time to get rid of water,,
But an engine that is running at 170 to 180*f coolant temp, is getting its oil to 225to 235*f anyway,, so as long as it can get up to 170* coolant temp fast enough & it doesn't take too long to get there it will be fine, I still think best temp to run a rover v8 for the sake of longevity & avoiding unwanted wear & tear (specially liners & head gasket) is around 178 to 185*,, is it possible, perhaps with right inline mod & right thermostat,,
I am not saying an engine running at 200-210* will blow up, but definitely will shorten it's life & more maintenance is required, some of us consider changing head gaskets as normal maintenance in these engines,,,!
Could it be because they run too hot from what they were originally designed to run,?
i know some will say they ran their trucks for X-amount of miles & never had head gasket problems, because they did good maintenance , but from what I see in this forum,, most trucks have suffered from this issue more than once,,, & their owner did regular maintenance as they should,, but maybe they were running at temps that are considered normal by factory,, (195 to 210),,
(High temp was essential for these old designed engines to pass pollution regulations of new era),, and even weakest engine will last long enough (when new) to pass warranty time period, at least most of them would,, and after that you are on your own,, not many ppl bought extended warranty on these, but whoever did, won big time ,,,