[sick472]

All the older (pre-72) vehicles that I have had the pleasure of owning would puke coolant after shut-down...IF it was filled all the way to the top. Try this, let it do it's puking a time or two (if it even needs to puke twice), let it cool, look into the radiator and do not fill it over that mental mark. Typically, I find that the appropriate level lands at the top of the fins.

I'm not saying that the 7psi cap is appropriate as all of my older cars have that 15-16# cap. Changing it to a 15-16 cap will increase the boiling temp of 50/50 coolant by about 22 degrees F. This helps IF you car tends to run close to 268 degrees F and is actually boiling the coolant....BUT, it your not running that hot and not boiling your coolant...the coolant will still expand at the same rate when it gets hot regardless of the cap pressure rating (within reason). I would bet you are not boiling your coolant, just heating to up. This causes fluid expansion and you just don't have anywhere for it to expand. Leave some room in the radiator for it to expand or add an expansion tank.