WTF two new seperate thermostats not working+ more input needed

[Swearbody]

What a frustrating day. I got the engine running today and couldnt get it to stop trying to overheat. Tried all the usual suspects starting with the thermostat...went through 2 thermostats and finally just ran it without so I could break the engine in. Both thermos wouldnt open for some reason.
Of course this was all after the fire that erupted from my header due to the oil sender leaking through the body of the sender. Luckily I had an extinguisher on hand. I had to just plug the hole in the block and am hoping that I dont need the oil sender next to the filter. I dont even know what its for to be honest.

 

[legopnuematic]

Believe the second sender is for electric choke, no pressure, no power to choke coil, so if ign is on and truck is not running it wont use power to keep choke open.

 

[Swearbody]

Believe the second sender is for electric choke, no pressure, no power to choke coil, so if ign is on and truck is not running it wont use power to keep choke open.

Ok thats ok for now then. Ill run a lead to the choke or bridge the connection later. Im just trying to break everything in for the time being. I didnt think it did much considering the engine fired without it.

 

[fast68chevy]

Ok thats ok for now then. Ill run a lead to the choke or bridge the connection later. Im just trying to break everything in for the time being. I didnt think it did much considering the engine fired without it.

use ign spade connector in fuse panel to power the choke, new wire directly from there to choke. easy. are you sure its not another cause? put the thermostats in a pan of water over 190 degrees around 200 or 210 and see if they open. make sure spring end of it is pointed inside intake manifold. pointed end of thermostat up towards hose. if thermostats is not opening then one hose will be cool or barely warm and other one wil be hot. have you done any other work like water pump swap or intake gaskets or fan swap or anything? when does it over heat exactly? when sitting not moving? or when driving down road, or both or?
does cooling system build up good pressure 15 to 18 PSI ? need that pressure to help cool. compressed water is lower temp.
have a good complete intact fan shroud and fan spinning sucking air through radiator good?
ive even seen where the wrong water pump and or fan from an '87-up motor is swapped on, which is reverse rotatation but they look identical.

 

[Swearbody]

use ign spade connector in fuse panel to power the choke, new wire directly from there to choke. easy. are you sure its not another cause? put the thermostats in a pan of water over 190 degrees around 200 or 210 and see if they open. make sure spring end of it is pointed inside intake manifold. pointed end of thermostat up towards hose. if thermostats is not opening then one hose will be cool or barely warm and other one wil be hot. have you done any other work like water pump swap or intake gaskets or fan swap or anything? when does it over heat exactly? when sitting not moving? or when driving down road, or both or?
does cooling system build up good pressure 15 to 18 PSI ? need that pressure to help cool. compressed water is lower temp.
have a good complete intact fan shroud and fan spinning sucking air through radiator good?
ive even seen where the wrong water pump and or fan from an '87-up motor is swapped on, which is reverse rotatation but they look identical.

Every wire,gasket,hose,line,etc has been off recently. I just painted the engine bay,replaced everything with new, dropped newly built engine in. All aforementioned points have been checked off as completed. Engine is now holding 190 and actually was the whole time. Its either the sender or gauge. I have an aftermarket sender and gauge on the head now and have verified temp with a infrared.

 

[Bennyt]

You can also check the thermostat by heating up a pot of water and watching the thermometer to see when it opens. I still like to drill 2 "weep" holes in them just in case.

 

[Salty Crusty]

Air pockets under the thermostat and in the intake will cause significant delays in thermostat operation. It will usually eventually open but nothing like when it's touching water.
I always break new engines in with no thermostat, add it when I dump the break-in oil.