Yep I agree about not boiling it in anti-freeze, it will turn black and its hard to scrub off with cleaners. That happened to some other parts I had when I first bought my cheapie crock pot and was not used to the heat settings.

Ultrasonic cleaners are one of those items I always wish I had but always on the bottom of the need list, and I never really come across the solutions seperate, because I've always wondered how they would act alone on rust and other oxides. Its good to hear you have good luck with it on the rust in bearings. Thats something I will keep in mind.

I sprayed and wiped down the case with WD-40 so far with nothing comming off in my rag, thinking I would start with the mildest of chemicals this motor will commonly see. With it being a boat motor, WD-40 is used quite commonly as a flush agent after a dunk. The hull for this motor isnt started yet so it will be awhile before I learn what effects nitro and heat will have over time. If it starts to come off I will have to try and remove at least internally so it doesn't wear the piston.

The heating and air conditioning trade have what they call a de-smutting agent that will strip aluminum down to a bright finish after a round of corrosion, but it would take hunting some down and dont think its very inexpensive or sold in small quantities but thats a thought. Who knows what happens to sizes though when that is done. I'm pretty sure it is simply an acid. I dont know of any other types of "etching" agents to remove contaminates or oxides without having to scrub.