I want to rebuild my original date coded alternator for my 70 cuda. The internals will all be replaced because they are rusted together, so I will be using just the two case halves. What do the rebuilders/restorers use to clean up the crud on the aluminum case without removing the date codes. Beadblast, Sandblast, Walnut shells? I want it to look as original as possible when done without painting it.

Similar to cleaning a carburetor. Media blasting is as a last resort only, it can (will) permanently damage/change the texture. Most restorers use chemicals to clean away grease and oil then a dunk in a sonic cleaner. Final cleaning with chemicals and then a tumble in various "soft" abrasives for the final clean up. Sometimes a REALLY degraded or bad casting will require blasting, but as a last resort only. Start with soda blasting and move towards more aggressive media as required.

.02

Send it to Dixie Restorations.

Painstakingly done with never-dull, simichrome/flitz and the worse stuff with barkeeper friend and a toothbrush, followed by previous.
A felt wheel with a dremel or foredom helps.
Keep in mind this will keep the as cast surface and slight patina.
I've used vinegar or stronger acids (straight or dilute muriatic) reserved for the worse cases, generally wheels or other parts left out on the weather..

OK I have it soaking in degreaser now and will see how the chemicals work. If it still needs more cleaning after that will try the dremel with the felt wheel and then the soft abrasives if needed. Thanks for the help.

What are you looking for? OEM level of resto, or just a rebuild? If you're not wanting to send to Dixie for a correct job, then find somebody that has a vapor blaster to do the case, that will do a very good job on the aluminum with out messing it up. But as mentioned, Dixie is the best.

I just bought a rebuilt alternator, AC-Delco. It had a surface so pitted from sandblasting that it sparkled in the sunlight. Remanufactured in China. Factory numbers stamped into the case were obliterated.

I painted it with clear to keep it from becoming a grease magnet.

Blasting IS the last resort.

R.

i own a vapor blaster and alternators come out very nice but a bit too bright for a OE application. they do dull in time but pretty bright.
Did the factory use a vibratory tumbler for finishing or was the finish a "as cast" thing?

With a glass bead cabinet, the pressure can be turned way down so that it takes a long time to blast the crud away, but it leaves the surface very clean and about the right color and texture.

But the only way it will stay that way is to coat it. I use clear with flattening agent. It takes some experimenting to get the right amount of flat and it probably does not look 100% OE correct. But it looks very much like OE to most of us. And stays that way.