Re: Fuel pump heat shield

Posted by Fred Puhn On 2013/8/31 19:27:52

The heat shield as I understand it is a sheet metal part that does not touch the fuel pump or the exhaust manifold. Therefore the heat shield is supposed to block radiation heat transfer between the hot exhaust and the fuel pump. Radiation is heat flowing across a gap, similar to the heat you feel from the sun. Radiation heat transfer depends greatly on the temperature difference between the hot and cold objects and to a smaller extent on the emissivity of the two object surfaces. Emmissivity is a property of a surface that depends on things like color and gloss. The highest radiation heat transfer is to or from a dull black object. The lowest radiation heat transfer is to or from a shiny surface like chrome. I am sure the temperature of the heat shield would be lowered if its upper surface (or the manifold) were polished and chromed. If the heat shield is cooler the radiation to the fuel pump would be reduced somewhat.

A sheet insulator on the bottom side of the shield would lower the shield bottom surface temperature a bit. However I think a shiny top surface would have a greater effect. Some thermal analysis or testing is in order to get numbers.

The biggest effect by far is having a heat shield on the car instead of not having one. Perhaps that is why Packard did not bother with polishing the heat shield.

Also on my fuel pump there is no insulator at all between the engine and the pump except a thin gasket. There are no bolt insulators. Does anyone sell those missing parts? I am sure I could make them if I had the required insulator thickness. Putting an insulator between the pump and the block would also change the action of the fuel pump. Does anyone know what this does, good or bad?