It could be a sticky thermostat or one not opening fully. I have had it where most of the time it is OK but a little bit more work from the engine and the water flow is not enough to keep it cool, and the temp heads up very quickly.

I have a 6 Blade Steel Fan and hi-flow Thermostat.on mine as well as a small Overflow Bottle tucked in next to Regulator. I can fill Rad to Top. Every little thing helps to keep it Cool. I also removed the Air Deflector from top of the Radiator.

  

I guess it had to have, that or like someone else said it water locked.

Mine has a problem with cooling down after a long idle, usually not at a light but if I'm waiting in traffic or in a line of cars. But also it has a problem of getting hot trying to drive on the highway. The car will get up to 180 and stay there for 10ish minutes where I'd like it to stay, but sure enough it'll start raising up to 190 slowly. Sometimes it'll slowly go back down to 180 again and wobble between the two but sometimes it'll keep going up and I'm forced to get off the road and let her cool. If you guys are suggesting I change fans I might as well change to that smaller pulley while I'm at it. Can you point me in the direction of where to get one of those pulleys?

I think you were just low on water the first time around. Opening the lower hose drains things pretty well, maybe even some out of the heater circuit. You were low enough on water that when everything refilled the radiator didn't have enough in it to cool, you got to boiling, and the pressure pushed more out. If it won't overheat now, and give it a couple of heat/cool cycles, make sure you've got heat from the heater (showing it's filled), check it for full (see DLR's comment) and go for a ride.

Remember if you've got an overflow tank and it's full, a full radiator will overflow the tank when it warms up.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

Half...... I’ve not had one on my 56 for 7years I’ve owned it. I fought overheating for 5 years before Greenbird here said to put on a smaller water pump pulley. Mine was mostly an idle problem and getting it to cool down after a long signal in 85+ degree weather. I didn’t want the look of one and our family owned 2 yblock 55-56 Fords when new and never ever had a overheating problem. Factory at that time was 1” low and it still works today.

56 Vic, B'Ville 200 MPH Club Member, So Cal.

Okay, well I do have an overflow.

If you don’t have an overflow tank you need to leave the water down at least 1” for expansion with whatever cap you are using. I believed the original was #7-9 but a lot of older cars I’ve seen have #15.
May not be your problem but if I don’t leave mine down it will dump it on the ground out the overflow.

56 Vic, B'Ville 200 MPH Club Member, So Cal.

Well no, I just refilled it till it was full again. I knew that it would need more once the engine had ran some because I still had like half a gallon left in a pan on the floor but I figured what would be in there already would be enough to get by on and I'd just come home, let her cool off, then add the rest and burp it later.
I actually constructed an overflow tank out of a mason jar but that tank has an overflow of its own too. I found out after I went to the trouble of constructing it that it was apparently a waste of time I guess. : /