Originally Posted by lazlo
I notice on protruding tabs, bolt holes, and smaller "things" that there will be more porosity and it seams I see more broken off stuff with these castings than others. I know the styrofoam "look" doesn't go very deep but it goes plenty deep enough to be impossible to get perfectly clean for a TIG weld. These castings will have more voids and cavities than other "normal?" castings.
The last thing I saw with this kind of casting is OMC outboard motors. The head I used on my 60hp rebuild had visible voids, craters, and weird spots even right in the combustion chamber. There were places in the water jackets that had holes where they shouldn't be and casting where there should have been holes.
I don't know what this guy did to this head but you can see the porosity of this OMC head.