Re: New 390 smoking
did you get the head gasket on right. It looks like one is going on wrong but you need to make sure that the water can flow. The water comes through the block and up to the head at the long opening, then forward through the head and into the front of the intake and into the radiator. If you put the gaskets on exactly the same you are going to have problems. either way you look at it the head has to come off.
Did you do any porting of the heads?? If you grind too far and weaken the port it could spring a leak. Take the plugs out of the side thats smoking and crank the engine while someone watches and see what comes out.