The cases I recently obtained are sound but heavily oxidized. Now, to clean them inside and outside, what shall I do? The outside is no problem: bead blasting, but the inside is another thing. I think I'll bead-blast that too, and then wash several times in a dishwasher to get rid of possible beads trapped in the surface.
Good/bad idea, suggestions
There are no facilities that I know of that use walnut or cherry grit.

email (option): viaconsu # planet dot nl

I cleaned mine repeatedly in an ultrasonic cleaner and then scrubbed them with 'Scotchbrite' lubricated with any household cleaner that I could find marked 'do not use on aluminium' ! - What this means is that it'll stain stuff in the kitchen.

I've heard good results from soda blasting and it washes away in water. Personally, I would never contemplate bead blasting where oilways are concerned.

Bead blasting bearing surfaces isn't a very good idea too I think.

email (option): ahum@quicknet.nl

The oilways in the cases are negligeable, you'd clean them out even if you weren't blasting them. personally I'd go for vapour blasting (as I know what the cases are like) as it tends to pick up less oily hand prints during the rebuild and they keep cleaner for longer. If you can't get the vapour blasting done I'd sandblast them first to open up the pores in the metal and then bead blast them .

email (option): davmax@ntlworld.com

I always blast cases inside and out after degreasing etc...first with aluminium oxide and then glass bead to finish.
The key thing is to very thoroughly clean them afterwards. I've never had a problem with residual blasting media..Ian

email (option): ian@wright52.plus.com

Thanks guys, now I know what to do
And for the bearing surfaces: the old bearings are still there and will be removed after cleaning!

email (option): viaconsu # planet dot nl

Working with aluminum cases over the years I have tried most of the popular methods - engine degreasers and water, as well as various media. My best results have come from vapor or soft media blasting such as walnut shells. They don't distort the surface which keeps the original finish as intact as possible. Also of course, no real worries with a small bit hiding in a corner coming loose on initial running wreaking havoc in any important areas. I personally have not had a problem with left over media causing an internal problem in an engine, but I suppose it could happen.

I never liked the look of aluminum cases which have been bead blasted. It looked wrong. And I hated how easily it was blemished by oil afterwards. Once after bead blasting, I used very fine steel wool to work the surface back to a more original look and that wasn't too bad.

I don't know who you take your cases to but the place I took mine was agreeable to put media I brought into one of their small blaster cabinets. I purchased the walnut shell media at an industrial supply facility.

One other thing I didn't mention is using ball peening or burnishing which uses approximately 3/64" irregular hardened steel balls and is either rolled in cabinet (similar to the way metal detectorists clean their coins in a rotating barrel) or in a similar machine to a rotablast cabinet where the cage like "barrel" rotates inside a cabinet whilst paddles flick the media at the rotating cage. This is the best finish I have seen, but few companies use it. It gives a slightly shiny "as cast" finish and the balls are so big there is no chance of missing one when cleaning the media out.
I think it works best on stuff that is clean in the first instance, so you may have to sandblast them first

email (option): davmax@ntlworld.com

The glass bead I use after the Al. oxide is only used to produce a surface finish. It too gives the slightly brighter 'sheen' which is easy to clean oily finger prints off..A little WD 40 on a soft rag takes oily marks right off after assembly...Ian

email (option): ian@wright52.plus.com

You could also dry ice blast them. It doesn't blast away the alu as much as bead blasting does. However, i heard that dry ice blasting doesn't work too well on heavy "rusted" areas as the rust penetrates the alu deeper than the dry ice blasting can clean it, which means at one point it will surface again. Another nice thing about it is that i only leaves water.

email (option): kschaank@hotmail.com