You can’t trust thermostat ratings
Or am I missing something here?
I think yur spot on.
The water in the block is at say 180 to 200. The combustion temperature at idle might be 500, at WOT maybe 800/1000.. But by the time the expanding gasses have done their work; ~1/3 of the heat has been converted to energy, ~1/3 is going out the exhaust, and ~1/3 is transferred to the cooling system.
You wanna keep the heat in the head (as opposed to down in the cylinder walls), as much as possible, cuz the water up there is already hot and moving towards the rad. If you start the burning process too late, then the cylinder will get too involved, sending even more heat into the block, and HOTTER water into the heads.
So, yes you gotta move that heat, as quickly as possible cuz in a few milliseconds, more is coming.
If the water boils next to the confines of the chamber, it can no longer absorb heat, so it has to be kept moving. The slower it moves the greater the chance that the molecules next to the hot surfaces will boil, which will disrupt all the molecules around it, until it settles down. This is a bad situation.
The internal surfaces of all the engine have to be kept below the boiling point of the coolant. NOT all of the coolant is at the same temperature all of the time. The heads are the hottest.
The piston crowns likely the next hottest and they are not even in contact with the coolant! If the pistons swell up, it's gonna take away power from the crank. You can't let that happen.
If the pistons get too hot, you can bet they will share it with the rings, and if the ring-gaps close up, that will take power from the crank. You can't let that happen. The coolant cannot be allowed to boil, no matter what. I'm not talking about boiling in the rad; but rather boiling anywhere next to the heads and water jackets. So by your finger-in-the-flame analogy, it better be kept moving.
But there is nothing wrong with running the Minimum coolant temperature, as determined usually by the thermostat, at any temperature so long as the coolant next to the hot surfaces, never boils.
Because I have alloy heads, I chose 205.
I run a 7 pound cap, cuz my system is ancient, and it survives. Heck my rad is a 1973 model with patches on it's patches.
But I depend very heavily on that 7-blade, hi-attack angle, all steel fan and the thermostatic fan clutch, to not let the coolant rise much past 205.
and the hi-flo pump helps with that.
and the roadrace oilpan has a lot of radiating area, plus extra oil in it, and the cylinder wall squirters are working, and I send extra oil to the valvesprings. So all of these measures ease the load on the cooling system.
Yabut some of those measures cost me power right? So does damaging an engine, even invisible damage inside the cylinders, that you don't even know is happening until she starts to blow oil.
My car was a DD for many years, and so a few hp lost is/was cheap insurance. She now has well over 100,000 miles on her so I think it's working.
