Bead blasting the only solution?

[andyvh1959]

I have some vintage motorcycle crankcase covers, die cast aluminum, that have a good bit of discoloration I cannot rub out with steel wool/WD40, or Mothers, or Chemical Guys metal polish. I'm thinking the cover first needs to be bead blasted of baking soda blasted, and then go to the polishing stage? Any restorers out there with suggestions?

I have a top feed spray gun I could pour baking soda into it and use my air compressor to soda blast the covers outside (don't have my HF blast booth set up yet).

 

[rjacobs]

I had some aluminum cylinder heads vapor honed. Does NOT remove material...supposedly. I can still see casting marks so I tend to believe it.

Head on the left had been hot tanked only, but it didnt do much except remove the caked on oil and grease.

 

[MileHighRover]

Vapor honing is the correct answer.

 

[larry4406]

@Keyblazer built a vapor hone machine and documented some fantistic results.

Search his “what’s going on in my garage“ thread I believe it’s called.

 

[Stuart in MN]

NAPA stores sell a product called aluminum brightener that works well to remove stains and discoloration. I've used it with success on engine cases, but on smooth side covers like that they will need to be polished afterwards. It's a harsh acid so wearing PPE is a must.

Bead blasting or vapor blasting will remove the staining but they will also rough up the surface, so you would have to go through a series of sanding with finer and finer grits with wet or dry sandpaper to get them back to the point where you can polish them.

 

[kabinenroller]

I prefer not to blast any vintage engine cases because you lose the original looking finish. Soda blasting may be an option but I would do a test piece first. I normally clean the parts with a petroleum base cleaner, and do not use any type of abrasive pad. If you are looking to make the engine look factory correct polishing is not advisable, when I see a vintage motorcycle that has been “restored” and everything is bright and shiney I think that someone over Restored it.
PS. If you soda blast outside stay away from your lawn and any bushes, the soda will kill grass and small plants.

 

[yhprum]

Vapor blasting (same as Vapor honing is a good option, but it really depends on what the final finish should be. If it is polished, you could chemically remove the oxidation and then buff polish if that’s what you’re after. The Vapor blasting leaves a smooth satin finish.

 

[CraigStu]

Beed blasting leaves a very nice finish IF they use new beads. If they keep using beads until the disappear you get a sandblasted finish.

 

[no704]

As a young man I had a job at a corvette restoration shop. Boss gave me a pair of valve covers to clean. I polished them up really nice. He was pissed and sand blasted them back to the correct finish. Oops!

 

[BillK]

Bead blasting, soda blasting, vapor blasting etc is not going to get any pitting out. What do you want the final finish to be ? You mentioned "polishing" it ? If that is what the plan is you might as well get the 400 grit or maybe finer wet or dry paper out and go at it.