Any freshly rebuilt engine will run hotter than normal due to the tigher clearances at least until it is broken in. Extended stationary running while breaking in a new cam and setting timing, carb, valve lash, etc will also contribute to the problem.
I usually setup a big shop fan to blow into the front of the radiator to help keep the heat down.
I usually setup a big shop fan to blow into the front of the radiator to help keep the heat down.