A LOT of factors can enter into how hot your car runs.
It may be a cheap radiator. Brassworks (high end rad) sells various fin layouts and configurations to attempt to cash in on those who feel they may have a problem.
Or you may have combustion gasses leaking into your coolant at the head gasket. This can make a car run hot.
And others have mentioned that too high a flow through the radiator MAY contribute to overheating (the most resistance to removal of heat is the air itself and too high a water flow gives insufficient time for the water to cool as it passes through the radiator.) Many cut down their impeller or put other restriction into the water path to slow down flow.
And your engine timing has a LOT to do with efficiency and heat release. Check this first (and learn how to time the engine properly by reading up on Marco's best technique.)
And Ford tended to run hot anyway. Model Ts are considered optimal if on the near side of boiling over - their engine theory is derived directly from one lunger convention with a boil to cool heat transfer mode.
Your avatar is your car? The 30-31s have a slightly larger radiator for a reason and I'm surprised you're having a problem.
Still, a new radiator from any reputable source (maybe this not) shouldn't be having an issue.
There are some china sourced aluminum radiators now being sold on Ebay and elsewhere - but I would consider these not credible, not to mention not reputable.
Tell us more on what you've done to remedy this, if you have.
Joe K
