is this a blown head gasket ?

I have a 66 barracuda with a 273 2bl carb. after it warms up i've noticed that I have pressure built up in the radiator .I'll take the cap off and the water boils out . I checked the water temp and it said 185 .also the gadge read normal. I'm thinking that I have a blown head gasket? There is no water in the oil ,or on the dip stick ,filler cap. I've replaced the water pump last year and put a new thermastat in at that time and all was good till about 2 weeks ago . What do you guys think head gasket ? I'm a car guy but the more info the better old tricks are the best tricks. Thank for the help
Don