You might also try this remedy that a friend of mine was told about , tried , worked good . Take off the water inlet on the side of the block, cut a peice of sheetmetal the shape of the inlet neck. Drill 2 1/4' holes in the center of the plate, reinstall. What it seems sometimes happens is the coolant purculates alittle to fast and the water in the radiator does not have time to cool off enough to help keep the engine cool.