Overheating Issue - SBC

[Norm reynolds]

From what you posted it can be 2 things water pump going bad and the # one thing is air in the system I all way found getting the air out a challenge but a friend turn me on to a
spill free funnel What it does it goes on top of the radiator and you fill the radiator up and tun the car ( leave coolant in the funnel) as the car warms up air will be released in the funnel It does NOT make a mess and after the air is out let the car cool down what coolant is in the funnel will get sucked back it to the radiator
I got mine on Amazon for about 26 bucks
after years trying to get the air out of a cars radiator I have found that this is one of the best ways to get the air out

got mine here
funnel