Running white hot

On a cold motor check your heat riser flapper. Triangle lever looking thing on left side of exhaust manifold right under carb. It should pivot easily and actually bounce once it's wound against its spring. By default a cold riser valve will be in the 'blocking position', diverting the exhaust up to the bottom of the heat stove under the carb. When the manifold gets hot, the spring relaxes and pulls the riser position to the bypass position directing exhaust straight down the manifold to the head pipe. If it's stuck up in the cold.position it will really heat that intake up, not good. A lean carb (intake leak) will cause a hot combustion chamber/motor as well. And of course a sheared/rotted impeller or rad blockage/frozen Stat will cause a motor to run hot.