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Before I re-built the top end of my 400 and replaced the heads, stock intake and carb my engine coolant temp was always consistently normal.
Now with the new (Rebuilt) factory heads, Edelbrock intake and carb I noticed that my engine will run warm then cool off or it will stay too warm but never overheating. It seems to have a mind of it's own sometimes. I have replaced the thermostat and that helped. Typically if I'm on the freeway that's when it will run warm. When I get off the freeway onto the city streets it will cool off. I just have the factory temp gadge but mid point should be 180 to 200 Deg. When I run "Warm" it sits just below the high end of the normal. Someone made off with my good Snap On engine coolant temp gadge so I can't really test it accuretly unless I snag the cooking thermometer and make my wife upset at me.
I have a broken fan shroud but that wouldn't explain the freeway temps however I will replace the fan shroud. I'm also using no mix antifreeze and I have a new radiator. I also hold good pressure so no leaks. This is an F350 so it has the really good monster radiator that I have to pull a bank loan so I can fill it up with antifreeze.