I cleaned the Dnepr heads with come sodium hydroxide, nitric acid and water to remove the oxide that was present on the castings. I use the caustic soda to loosen the oxide, I then dip it in water and then into nitric to remove the smut that is the oxide on the surface and then into water again. This combination does a great job of cleaning the surface and getting me one step closer to a clean head. One of the heads appears to have a heli-coil of sorts using a brass insert to repair the threads in the spark plug hole. The other head has a a nasty looking compression chamber and at first glance I though it had dropped a valve at some point, but after cleaning I think it looks like evidence of a bad casting. This looks similar to some of the aluminum castings I have seen in a casting class so that's what makes me think that is was a bad casting. As you can tell quality control must have been an afterthought in the KMZ factory. I have seen some folks who have done considerable "porting" and combustion chamber clean-up, so I may need to look into this or have a go at cleaning and filling in some of the nasty surface.