welded aluminum head leaking, on car treatment?

[Dragsinger]

This head was on an engine that broke a rod, chamber was damaged. Head was repaired but now I have "milk" in the valve covers.

Do we know of any chemical treatment that might seal it? Engine is still together and runs fine so I thought I could at least attempt a fix before tear down and redo.

I have a Scotty School race date in three weeks so it's a chemical fix or miss the school.