Overheating Issues!

Can you drive on a flat road at 45 mph (A/C off if you have it) without overheating? Any car should be able to do this without a fan, as long as the outside temp is not crazy hot. If it still overheats while driving like this, there are a few things to look at

1. clogged radiator
2. incorrect timing, retard the timing enough and it will overheat.
3. combustion gasses entering cooling system, possibly from a bad head gasket