From the Vintage Japanese list:

A while ago, Chris posted a message asking about alternative methods for cleaning all the crud of aluminium engine parts

….here's one to try… Grab yourself a large saucepan, big enough for the item to be completely submerged, fill up with water and cut up 2 or 3 lemons in small pieces and put into the water. Bring to the boil and then turn the heat right down and simmer for up to an hour.

I tried this on my fuel petcock and it cleaned all the crud off in less than 15 minutes. It almost looked like it was bead blasted ! ! ! Well almost….When you pull it out of the water, your fingers will get smudged with grey “slime”…..just rinse completely and very thoroughly and then use a commercial  aluminium cleaner and you will end up with a mirror like finish….try it on a spare scrap part, you will be amazed how well this works.

And to protect it::: (from the Brit Iron list)

About aluminum engines: many OEM's do not paint aluminum engines (or components). Rather, they use a wax emulsion spray on the finished engine assembly. This works well as an anti corrosion film, but can be washed off with harsh solvents.

For hobbyists like us, I found another offshoot of the aircraft business that works beautifully: Boeshield. This product was developed by Boeing. It replicates the OEM wax coating.

Boeshield is an aerosol thinner/lubricant/wax in aerosol form which does a wonderful job sealing and protecting clean metal surfaces. Looks good too. Spray it on evenly after cleaning and thoroughly drying the engine.

Mask pulley surfaces. Let it dry for 4 hours, then apply a second light coat. The result is a durable clear finish which seems to last indefinitely. I use it for SCCA 911 motors, which are always being recleaned and worked on.

Also on motorcycles and marine engines. Gunk flushed with cold water does not seem to take it off, though solvent and steam cleaning will. The good news is that it is very easy to reapply and touch up.

Does a nice job sealing ignition systems, as well. Just for grins, I sprayed one side of a new aluminum Danforth anchor with it a couple of years ago. The results were so good, I have now cleaned and sprayed the other side, and the rode chain.

I have seen plenty of examples of painted aluminum engines. Most are a mess.Even the OEM (mostly older Japanese) clear coats fog up and lift, trapping moisture under the edges.

I think paint is OK for cast iron and steel stuff, but suggest you try Boeshield for aluminum. It is available at marine stores (eg, West Marine, about $15). A little goes a long way.

Hope this helps.

If you try any of this, I'd like to hear how you do…