head gasket or ring?

Do a compression check. When the low cyl. is found do a leak test. Put air pressure in the cylinder with it on top dead center with both valves closed. If the air leaks out of the crank case its the rings. If it leaks out of the radiator could be head gaskets. If its comming out of exhaust or intake could be a burnt or bent valve or a head gasket blown between next cyl.. These are just some test to narrow it down before tear down.