The poppet/t-stat housing has to seat firmly against seal in head, leakage will cause the leaking side to run hot. It is normal to see the starboard side to run 10-15° hotter than port.
Needs torn down, that cylinder bored and possible the others depend on how they "mike" out size wise. After you fix the result, you need to address the problem as that is preignition, either coil/pack ot timer base problem
Cannot set timing on a 60° motor with timing light, the flash will cause the optical sensor to read incorrectly, must use analyzer. Joes method will not work on 60° engines
Replace the fuel pump diaphram and pull a carb bowl drain screw. Let the fuel filter thru a white paper towel. If it leave black specks fuel lines in engine need replaced as they degrade from the inside
