How to clean your engine cases

I recently read that some folks like to use "oven cleaner" to clean up their engine cases. Warning! It's a bad idea!!

Also, don't polish your engine cases. Hard to keep clean. Not original either. Just clean them up or bead blast them, which is what I did.

I have had this discussion before with my mentors and just emailed them to confirm that I was right.

Here's what Tom G. said:

Bad idea.

Cases are aluminum, and most oven cleaners are
lye-based (caustic soda).  Lye reacts with aluminum.
Frankly, I don't know if it weakens it or not
(probably not upon temporary surface contact), but it
does leave dark stains on it.  Ugly.

Scrape as much as you can with a plastic, wood, or
even metal scraper, and then wash the residue off with
solvents.  Not necessarily paint thinner either, but
ok to use it if you like.  Gasoline is cheap (but
explosive!), and there are proprietary parts washing
solvents out there which are less combustible, and
have additives to deter evaporation.

Here's what Christopher M. said:

I agree with Tom. If you buy parts washer fluid at an auto parts store,
avoid the Purple Power stuff. It creates some sort of effluoresence on
aluminum. Not sure if it eats metal, but it gets ugly. Easy to brush off,
though. I like the paint thinner that is listed as reduced odor. It still
stinks, but not as much as the regular stuff.