Safely removing oxidation from lifter bores/ main journals

[Chipbuster]

Hello everyone!
I have tried searching this topic , wit no success.
Can anyone recommend a safe way to remove the oxidation usually found on the main bearing / cam beating / and lifter bores ?
I picked up 2 solid cases at a swap meet , but they have been disassembled for some time and the machined surfaces have oxidized .
Would appreciate any experienced advice on how to properly clean the critical areas without doing any damage , or adding excessive clearance .
Thanks

[Ol'fogasaurus]

A copout answer would be to take the cases to a machinist to see how bad or deep the oxidation is and the overall conduction of the cases before you get too deep into them. You never know the whats or whys the have sat like they have. I got stuck with a couple disasters myself over the years so be sure before you throw too much work, plans and money their way.

[raygreenwood]

What you dont want to use.....is Scotch Brite pads. Mamy people do not know how those are made. They are not innocent plastic matrix pads. They are made with a serious abrasive molded in.

Removing just oxidization......you can use a very light acid solution to dissolve it. This is one of the few cases where I would suggest using something as dilute as vinegar/acetic acid. .....but while that works.....its very very slow and keeping these areas wet for days is likely to cause as many issues.

You can use ospho on aluminum and magnesium to remove white powdery oxidization safely. It will not convert the oxidization like it will for ferrous metal rust. I have used it for real mag wheels and transmission cases with no issues.....but try a spot in a non critical area first. Brush it on with a soft bristle paint brush....keep working it in for 10 minutes or so and then rinse off. Ray

[Ol'fogasaurus]

Good advice Ray but if there are any concerns... of any kind then see an expert. I have thrown money and time at a hopeless project when an inspection would have told me not to.

I also agree with the bit on the scotch brite pads, I am currently making pottery and a standard scotch brite pad removes, shaped dried clay just about as quickly a piece of P 130 sandpaper.

[Clatter]

OK, I'm confused...

Why would Scotch-Brite pads be worse than any other abrasive?
You are going to have to use abrasive -something- to clean heavily-oxidized parts regardless.

As long as it's rinsed away afterward, why would emery cloth or crocus cloth or wet/dry be any better?
Scotch-brite gives better control due to being more flexible.

While vapor-blasting or walnut shells or soda or plastic media blasting is preferred,
If you are going to be working it by hand, I'm failing to see the issue.

I was taught by some very experienced mechanic/machinsts to polish things up to get a good measurement.

It's SOP in my camp, here..

[Ol'fogasaurus]

If I remember correctly, at least at one time there were several "grits" of the Scotchbrite pad available but, if there still are, I haven't seen them for a while. If they are still available then you might have to go to a specialty store such as a paint or auto paint store to get them.

The last Scotchbrite pads I bought, for what I am currently doing (non-VW), compare almost as aggressive to the new P-150 grit sandpaper; maybe a little less so but still it pretty aggressive to softer materials. Remember that the material in the ACVW case is not what you would find in a cast iron block and you don't want to chance scoring the case. For instance, if you get too aggressive when cleaning out the lifter bores you could easily egg-shape or score them when trying to get the last of the oxidation out... for example.

Caution is only what I am suggesting here.

[turboblue]

Soda blasting works.

[raygreenwood]

OK, I'm confused...

Why would Scotch-Brite pads be worse than any other abrasive?
You are going to have to use abrasive -something- to clean heavily-oxidized parts regardless.

As long as it's rinsed away afterward, why would emery cloth or crocus cloth or wet/dry be any better?
Scotch-brite gives better control due to being more flexible.

While vapor-blasting or walnut shells or soda or plastic media blasting is preferred,
If you are going to be working it by hand, I'm failing to see the issue.

I was taught by some very experienced mechanic/machinsts to polish things up to get a good measurement.

It's SOP in my camp, here..

Its what the abrasive is made of. You would not use sandpaper on the case journals right?.....well the active abrasive ingredient in scotch brite pads is aluminum oxide. Same thing that is in sandpaper and grinding stones. Aluminum oxide is VERY hard. It does not break down and shatter as it abrades......so it takes off a lot of material.

As also mentioned soda blasting works well.....as the sodium bicarbonate is softer than magnesium. It mainly abrades by supplying constant volume at high velocity. If you get carried away with it though....you can still screw up soft metals.

Also as I noted....you can remove oxidization. ....only the oxidization chemically with diluted phosphoric acid.....which is the same chemical used in lime away for basically the same purpose. Ray

[christo]

Ray, so can I use Lime Away instead of buying phosphoric acid? also can it be used on powdery covered cylinder heads?

Thanks, christo