Flathead running cold

The holes are always tapped. Some were fitted with petcocks, others have plugs in. I've seen both.
 
On the next go round I'll fill the engine block through the water outlets to eliminate air in the system... after I drill holes in the stats, install hoses and hope for the best. Have to figure a better way to drain the system without butchering the grille. I'll check for a block petcock but not sure how that mitigates the antifreeze all over the floor. Really despise doing jobs over and over!
 
There probably will be 1/4 pipe plugs. Remove them and install drain petcocks. Use a hose and drain in to a bucket in the future.
 
You really want to fill the cooling system from the bottom to force the air out the top. This is normally what happens when you fill the system through the radiator cap, the coolant flows down through the radiator, through the lower radiator hoses to the engine and fills the engine from the bottom up. There should be a way for the air to escape the engine at the thermostats and up the upper hoses to the top tank of the radiator.

Regardless of how you try to fill it, the water is going to go down and the air is going to try to rise and may collect somewhere that is not beneficial to cooling.
 
What the temp when you insert a thermometer in the radiator. Ambient temp is a critical factor. Put a piece of cardboard over the front of your radiator and go for a test drive. My 296 loved the cold Menomonie, WI Wisconsin winters.
 

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Just recently my Flathead was puking coolant out of the top of the radiator and then running hot. I had the radiator rodded out and then it ran real cool as you say yours is doing.

I installed 180 deg thermostats and one of Skip's 4lb check valves on the overflow and on 'cold' days (temps in the 50's in Louisiana) it struggles to get to 180.

When the temps are in the 70s it'll get to 180 and the stats will open and then it will drop to 170ish and they'll close. So the temp bounces back and forth between 170ish and 185ish. I am ok with it since the summer(March - November) temps are upper 80's to 110, I am hoping it will run in the sweet spot in the summer.

Not much help for you but just saying your situation is not completely unique.
 
Must have that rare bird then but not wishing for the opposite scenario.
Remember my buddy having a 47 Mercury convert. that always ran hot. Over heated and refused to start. We were 16 and 17 year old kids and knew nearly nothing ...Geez, guess I haven't learned much since then! He took it to numerous mechanics and never did fix the problem. Pushed that sucker more than road in it. In spite of that have many fond memories of that car.
 
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