OK, here's my list: 1: radiator fins clear?
2: is the fan turning? are the blades facing the right way?
3: is your timing off?
4: block and rad flushed/clean?
5: are you losing coolant without leaking it on the floor?
(this is a possible head gasket. If you have anti freeze in
it and you are blowing white smoke it could be anti frz.
entering the cyls. and coming out the tail pipe).
6: do you have a water pump and is it working? non operational
pump could cause a blockage.