Water Circulation Issue

[defdes]

So I just disassembled the cooling system, flushed the bock, 2 new welsh plugs, flushed the radiator, new thermostat, put back the existing water pump as it looked in good shape and not that old, cut my own cork gaskets (.045?) used aviation sealer. I just went to refill the system, I got about 15 of the 20 quarts in until water started to back up the neck. I went and ran the truck for about a minute to circulate water into the block to make more room to top it off. When I shut it off, the head was hot (smoking a bit) and the coolant had not gone down in the filler neck. All was fine before I took everything apart, I was just doing this as a precaution for the warm weather that I hope that is coming some time in the next 2 months. Any ideas of where to start? Could those cork gaskets compress enough to restrict flow like that?

[fanboatman]

Would it be possible that you accidentally put the thermostat in backwards? Or maybe the water pump gasket on wrong? Not saying you didn't do it right, but even the best of us mess up every now and then.

[bilfman]

Maybe air locked in there.

[defdes]

How dare you lump me in with the best of us! Assuming that my home made gasket between the front of the block and the water pump assembly is not constricting flow and the thermostat is put in correctly (brass plug with temp. # is in the block).
I did have the petcock to the heater shut when I filled it, does it matter?

*EDIT: Opened the heater core petcock and that did, makes sense. Thanks for the tips.

[Cheyenne Dave]

There is an 1/8" plug in the head that can be removed/"cracked" to vent off any air. You want to open your heater valve as well.

cd