need head gasket help

Any tips on keeping head gaskets from blowing(Honda metal gaskets).Head resurfaced-cylinder top lapped and level-have tried using Halomar,Permatex,Blue hi-heat silicon,copper paste.Have torqued head bolts at 12lbs-15lbs-20lbs.Still blow all coolant out of water pump inspection hole after 15 min.New seals and shaft ok in pump also.Help