Classic/Antique Car Repair: model a radiator, combustion gasses, head gasket

Question
I have a 1931 ford model a coup. I can not stop the coolant from overflowing out the radiator. I thought the old radiator was plugged so I replaced it with a new one. Same result.Any ideas? Thanks Dave

Answer
several things could cause this a bad head gasket for one. when the engine is cold with the cap off cold you see the coolant bubbling it should not if it is doing this the combustion gasses are entering the coolant jacket. check this with a cold engine