Yes the baking was to get the oil out first, then we cleaned with acetone, before both those steps was sandblasting. Sandblasting and cleaning with acetone alone can not get the oil that is soaked in deep out but I bet the instant you strike an arc on it the oil will blow itself and molten aluminium all over your electrode. That is why you want to back it first.

We were powder coating so I did both bakes at I think 300 or 400 degrees for every engine piece and there was no distortion that I could see when I reassembled everything.

Good luck