Dies when hot, possibly boiling gas, exhaust flap stuck

Have a few things going on with a 65 170 in a valiant, has a NOS carb that has only been on it a short time, has the pertronix 2 ignition on it, fuel line is ran over the valve cover and not close to exhaust manifold, car starts runs great, seems to be getting pretty hot after just a few miles of driving then it will just bog way down, have to feather the pedal just to keep it running at a crawl and still dies, then will fire up for a hundred yards or so then bogs/ dies, when it was real hot today after bogging down and dying several times, opened the carb by hand and there was a lot of white smoke coming out of the top, worked the throttle to watch what happens when a lot of gas is given and just a lot of white smoke and heard boiling in the carb. Not sure if timing could cause it to get hot enough to boild gas, the main thing I am worried about and think it may be is the flap in the exhaust is stuck not sure how open or how closed but will not budge, worried about separating the intake and exhaust manifold and then separating the exhaust at the flange as I am pretty sure non of this has ever been removed, low miles car that was old lady owed. looking for suggestions, also what is the factory timing? 5 before tdc? appreciate any and all info, thanks.