Pressure build up in my cooling system

Hello guys,

Ive got some isssues. Just noticed this issue starting today. I bought a guys project engine a year ago. The engine was rebuilt by one of the local machine shops in his town. I have reciepts. Anyway the engine has sat awhile almost 2years completely assembled. The engine was never started. I installed this engine in my Dart [318] and it fired right up. The head gaskets started to weep water on the back corner. One corner on each head. I put some sealer in radiator and have seen no further leaks from the gaskets. I just got the car back from the paint shop and have had time to run it for extended periods of time. Now this is where it gets interesting. When I first start it cold after about 1-2 minutes the radiator hoses are hard [pressurized] way to hard for a cold start. After I relieve the pressure and warm it up with the cap off it does not do this senario. I can put the cap on and take it off without to much pressure. I think the combustion is pressurizing the coolant system when its cold. Its like the head gaskets are not sealing until it is hot. Should I re-torque the heads? Is this required on this engine? Should I just take the heads off and install new gaskets? No oil and water appear to be mixing. Radiator, t-stat,heater core,hoses,water pump are all new. Any help would be appreciated. Normally a head gasket is bad or good. If you pull the cap off when it is cold and start it no coolant shoots out the filler neck.


Ok I went out to start the car this morning. Itook radiator cap off and started the car. No water shot out of radiator neck like a blown head gasket. I put cap back on and started car back up. Ran for about 3 minutes and pressure was building up in the hoses. After four minutes I let off the pressure with the lever on top. [Car off] Thinking I had the pressure relieved I removed cap slowly. There was enough pressure still in the system to spray water over the RF fender. Do you think this is to much pressure to fast? Im thinking yes. I also grabbed the hoses and the upper hose was cold, the lower hose was warm not hot, and heater hoses were warm. I am thinking the thermostat had not opened yet to make the upper hose hot. with the new info do you still think it is a blown head gasket? I am going to go with majority. I just dont want to tear down a newly rebuilt engine if I dont have too. The engine only has about 2 hours run time. But it has been sitting 2 years. I am the only person to have run this engine and I have not overheated it.