so i know this is a super top secret subject but what is the process in getting a OE look to a alternator casting? Can anyone share the process?

Glass bead blast

Crushed Walnut Shells in the cabinet. Nothing else. Glass beads will etch the surface.

Glass beading is 2nd worst next to sand blasting. See if you can find someone with a water blasting machine, commonly called vapor honing. There is one man that can do it correct and that is Jim Ridge.

Agree with Jim Ridge for sure, and unsure if he does his vapor honed or another process. Once cleaned you should be using a Chem film on the aluminum, recommend Alodine 1001.

thanks guys. i own all those processes (bead, walnut and vapor) and none are quite OE looking. i dont expect a resto guy like Jim to give out his secrets but very curious. i know most carbs are done with vapor but not the finish i am after. thinking alodine time to experiment

appreciate the replies

It is tough enough to get an original look to the alternators, but it is even more difficult to keep it looking that way. That bare, open aluminum soaks everything up.

While not perfect, I glass bead the cases and then experiment with flattening agent in 2 part clear till I get the look I want. It lasts indefinitely and looks very near to original when done right. Been doing it that way for decades.

Just my opinion since I don't know the actual composition of the aluminum, but I have experimented a lot with cleaning alternators and Carter AFBs. Those alternators like the carter AFB/AVS have a zinc portion that seems to reside near the surface. Your never going to get the original finish. Period. In my opinion. You can't rezinc them nor get the original mold finish if you have to clean them. The elements and aluminum corrosion have taken there toll. They do not like the acid compounds used to treat other types of carb bodies.

The proper glass at the proper pressure is what is used on carbs and I have used it on alternators also. So you need to experiment. Tumbling with some of these synthetic materials also can change the surface and polish the aluminum, timing is again critical for the final finish you want.

I clean them with an alumaprep treatment followed by the Alodine 1001 (clear/white). Time sensitive and tends to darken the aluminum some the longer it is treated. But it is a conversion coating to help protect the aluminum.

A lot is dependent on starting with an alternator that has never been rebuilt to start.

That's not correct. Glass beads on softer metals is a form of shot-peening, like on harder metals. It's used in this manner sometimes.
It will 'smooth' out a surface rather then 'etch' it.

So if I have an NOS alternator made in 1970, exposed that way, it's surface will therefore not be as when first made.
Not like that NOS one has been hermetically sealed for 50 years.
So therefore it's still a crap-shoot as to what's 'original'.

Here's a couple pics of an NOS case

a couple more

This subject has been debated for years and years. Weathered, real world look vs how it came out of the package at the Chrysler plant. Here is another example of this situation; many of the suspension components under our cars were bare metal. Between the finished car sitting outside at the Chrysler plant, being transported on open transports in all kinds of weather, then sitting outside on the dealer's lot, what condition is 'correct' for those bare metal parts? Clean, fresh metal? Rusty? If so, how rusty?

And all of the lighter plating under the hood and such would also weather very quickly. The bare aluminum alternators would not remain looking like they had just left the foundry for very long. They tarnished and tinted without any use at all, just like the pics above.

A lot of guys subscribe to the 'as the car came off the transport at the dealership' component condition. But even that is a crap shoot. Our cars were shipped (for the most part) on open transports throughout the year and in all sorts of weather. So would the vulnerable components be the same on a car shipped in the dry warm summer vs one shipped in the dead of winter with snow, sleet, rain, and salt being thrown on them? Probably not.

So, pick your idea of the 'perfect, original' finish. The one that was installed at the Chrysler plant. The one that may have came off the transport. Or the one that was on the the car after just a little road time. They are all likely to be different.

It would be interesting to see documentation for the specification for over the counter parts versus what was done for assembly line. Regardless depending on how it was stored will have a dramatic impact on what it looks like, and how original looking it is.

wow! thanks Steve! that case looks like maybe its been dipped from the factory like a light cosmoline?

i appreciate all the replies guys. i am going to order some alodine and alumiprep monday and do some experimenting. ill post some before and after stuff and see what your opinions are.
i have two dry bead cabinets, one with #10 bead and one with #13 one vapor cabinet with #10-13 bead mix as well as my industrial equipment that i can do walnut, soda, glass, alox, epix, ect.

Sure looks to me that those parts are coated with yellow Alodine. I'm pretty sure Jim Ridge is applying yellow Alodine during alternator restorations.

About 10 years ago I sent Jim Ridge my double pulley alternator for restoration. Jim advised the case had been sandblasted by a rebuilder, was unsuitable for restoration, and he would need to find another that had not been blasted. He found another good case, and he took the photo below with double pulley in his shop at completion. Note the case finish with double pulley is without Alodine.

Later I realized my alternator should have had a single pulley, so I returned it to him to switch the pulleys. He told me that he had only recently learned Chrysler alternator cases had a finish different than the one he had previously put on my alternator. He said he would put the new finish on my alternator along with the new single pulley. The new finish is shown in the photo taken by me of the exact same alternator with single pulley. Unfortunately the lighting is not the same as Jim's photo, but I strongly believe that he had applied yellow Alodine. Note the hint of rainbow appearance.

Alodine is sold two ways, as a clear solution without dye, and also with a yellow dye added. In my experience, the yellow Alodine eventually dissipates in an engine compartment environment, but is easily renewed in place with a new brushed-on coating.

I can see how you may suspect Alodine 1201 but I’d place a bet on Alodine 1001 for the “added finish” bottom photo. To get the color in that photo it would have been in the bath for greater than a brief dip. Alodine 1001 will darken your aluminum a bit but leave it well protected, 1201 will produce a yellow to golden/brown color that is very apparent. I’ll state that color is the result of strength of bath and time in solution but 1201 would need to be diluted well beyond manufacturers mixing recommendations and dipped only briefly, potentially leaving the surface unprotected, and not a process adopted by a manufacturer.

I vaguely remember years ago that folks were of the belief the aluminum was bare, and believe Jim was of this position as well but changed some time later after rebuilding a low mileage alternator and/or starter and discovering there indications of protection on the surface, If you consider the exposure the aluminum on a starter body would experience during a salty/wet winter (anywhere but the SW), the aluminum body would degrade very rapidly. I realize this thread is about alternator cases but use the starter as an example due to its more severe exposure and like base material.

AAR is correct. Longer in solution the more the bright finish darkens. Alodine 1201 will turn the color more like a holley body. If you look at those alternators the texture has been polished and the originals were not polished just removed from the castings and machined an assembled.

Early on everyone seem to think Disc cars had yellow zinc MC covers because that is how a over the counter part looked. But they were painted black from the factory for assembly line cars.

I used to treat aircraft parts with Alodine. The one I used would range from golden to dark brown, depending on exposure time.
It sounds like some experimenting on spare parts is needed

Why has no one noted the differences in finishes and colors between the NOS case and the restored one?

Even the 'expert' restorer has had to make an adjustment on his finishes.

I do not believe anyone can tell us EXACTLY how all of the alternators installed on our muscle cars during the muscle car era should look. I will just bet that like so many other things Mopar, the finishes varied due to a number of factors. And that is before they actually met the elements.

One last point: My '71 GTX was awarded O.E. Certification at the '01 Nats. The alternator that I restored in the manner that I mentioned passed with no point deductions. I had consulted with Roger Gibson during the restoration.

Just my experience. Just my opinion.