Another way to avoid air pockets in the motor--just like a 400 Chevrolet (gasp, choke, puke)--is to fill the engine with coolant from the TOP first. Fill the radiator secondly. Start the engine and JUST AS SOON AS THE THERMOSTAT OPENS, fill the radiator to the correct level. A few of the 351 M and 400 Fords had the same problem--their coolant flows opposite to a 351 W--and, if filled with coolant like I have described, it alleviates the problem. It is a bit of a hassle, but it surely beats cooking an engine!