The valve covers on my original 273 Commando are basically in good shape, but are filthy inside with layers of gunk. The aluminum fins are in nice shape, and I understand that they are glued to the top of the cover. Normally I would have the machine shop hot tank the valve covers to clean them, but I think that the hot tank process would loosen the glue and damage the aluminum fins in the process. I have a media blast cabinet, but am not comfortable using it because I see no way of making sure all the blast media could be cleaned out. How have others cleaned these without damaging the fins? Is there a solvent that could be used that would not damage the aluminum or it's bond? My searches have not been fruitful, what have others done?