I'm looking to do some welding on an aluminum intake manifold.

The thing is filthy and I'm not sure the alloy but I'm looking to add some 6061 pieces and I'd obviously like to avoid warpage.

Any suggestions on how to clean the old piece up? Will just some surface grinding be sufficient or could the fuel/oil have pentrated into the material.

Should I preheat the manifold?

Any filler suggestions?

I'll be using a Syncrowave 180....Thanks