440 Mystery Thermostat Popping and Upper Rad Hose chugging

I have a 440 Tunnel Ram Fury with 10.5:1 CR, Stealth Heads, XE284H comp cam, 69’ Block 060. over. etc the full build is linked here: https://board.moparts.org/ubbthread...-ram-68-fury-build-opinions-welcome.html
Long story short it’s had this chronic issue of the auxiliary mechanical Temp sensor winding way up to 250+ degrees, followed by A chugging upper road hose and a popping and clicking thermostat, but the stock temp sensor is unphased. Not too long after the auxiliary temp sensor drops back down to 180ish and it’s all normal.. I’ve tried head replacement, head gaskets, thermostats, radiators, rad hoses, etc. I’m open to all suggestions but ultimately I think I’m gonna need a new block. I have confirmed combustion in the coolant from a sniffer test as well. Here’s the chugging upper radiator hose and a possible valve train tick/knock that had recently just developed.

- https://youtu.be/6lEKE8GadIM

- https://youtu.be/3udE4xoeF_I

As always thanks in advance for everyone’s help!

my first two thought were, are you putting the thermostat in correct side up, and what is it like with no thermostat at all?

The Thermostat is definitely the right way up and it’s got bypass holes drilled in it. The videos does the best job of describing the condition than I’d be able to. Also don’t want to run the engine much more until I get a hand on the engine noise end of things too.

sure looks like a bunch of air in the cooling system to me.

In the second video, That engine IMO appears to have at least 1 dead cylinder. that could be due to any number of things. I would start by isolating cylinders and proceed with the diagnosis once the cylinder is identified
You also mentioned valve train noise, could be a clue there

I also did not see any coolant moving in the upper hose, Maybe the RPM was too low ?

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I have confirmed combustion in the coolant from a sniffer test as well.

Time for a tear down IMO

Once I get a lump savings I’ll tear it down and send it out for a sleeve job, but maybe in the mean time I get away with just running it. I know from a compression test I’m making about an even 160 psi on each cylinder. Just would like an idea of how bad off the engine is. It’s a shame how well it still runs with all this stuff it has going on.

If you have combustion gas in the coolant, and you still have antifreeze in the motor, be advised, if antifreeze gets into the oil, it will take out rod and main bearings and kill a crankshaft in pretty short order.

When you did your compression test, did you do it with all the plugs out, or did you just test each cylinder individually? A cylinder with a blown head gasket can, and will show a higher then it really is, if it can use some of the compression from the cylinder next to it that still has a spark plug in it. Gene

Thanks for replies, the Compression test was done last week with all plugs pulled. No metal or milkshake in oil and the head gasket and heads are new stealths and cometic MLS gaskets. It’s still running 50/50 coolant.