Experimental test and theoretical analysis have been used to identify diesel engine valve heat flow in both conventional intake and exhaust valves and in metallic heat barrier intake and exhaust valves. Significant changes in valve surface temperature both on the intake fillet region and on the valve head have been achieved. A quasi-steady state finite element heat transfer analysis has been used to define heat flow by matching experimentally measured temperatures and temperature profiles. Heat flow on the intake valve fillet region has been changed with up to 90 percent blocked. Fifty percent of the heat flow from the combustion chamber side of the valve has been blocked with advance techniques promising 75% blockage.