Head gaskets, valley gasket, thermostat, waterpump, and radiator all just or recently replaced. Im not a factory trained mechanic, a laymen extreme actually. I have however followed the overhaul manual to the letter as much as possible without a testbook. Engine will idle forever and not overheat. 5 minutes at 1800 rpm or more the coolant boils and blasts out around the expamsion tank lid. When idling I can see circulation in the expansion tank. Other notes: gurgling or bubbling up from bottom of expansion tank at heater core hose connection. Sometimes top hose is hard and hot sometimes not. Hoses at both ends of thermo housing are hot, not untouchable but elevated. Also seems to be a doming of the valley gasket since repair. When engine finally cools down it takes on a gallon plus of water to refil. At one point the heater was not producing heat now it is. Its a constant tail chase for three days now. All this in addition to the days spent repairing. One last note, the repairs have drained my pocketbook so advice to just go have this or that $300 part replaced will only prompt tightening of the noose around my neck.
When it's hot/warm check the radiator for cold spots. If it has coldspots you need aradiator. Also if the fins are greenish in color and loose think about anew one. One last thing checkto see if you have the correct rad cap on it, they go bad and are cheap to replace. If you fill the system leave the cap off rad and taexp tank, fill sytem til full through expansion tank. Once full install rad cap. Then fill expansion tank once more. Put new O ring on rad cap andput expansion tank cap on. Let idle, then let cool down and open expansion tank cap and install more coolant if needed.