I have some old cast aluminum Holley valve covers that were grimy/dirty and had been painted at one time. I soaked them in my parts cleaner for a couple of days. Then I coated them with a citrus-based paint stripper from Wal-Mart. After that I shot them with brake cleaner and used towels and q-tips to clean them off.
Now they look really good but I need to buff them. I'm going to use a buffing wheel on my grinder along with some buffing compound. I expect them to look pretty good when I'm done.
I soaked them in my parts cleaner for a couple of days. Then I coated them with a citrus-based paint stripper from Wal-Mart
Old school version, clean all paint and crap off...stripper etc
The soak in a soln of cirtic acid...1 teaspoon per cup warm water
Citric acid will be found in the wifes spice cupboard, or spice shelf at the supermarket
Painting on and keep damp for a couple hrs, wash off
Good for restoring old vintage carbs, bell housing, anything Aluminum
I always use something to remove all the oil and residue first - a really good bath in the parts cleaner followed by an acetone bath. After that's all gone and rinsed, the citrus cleaners do a good job on anything water based. They're not effective on petroleum based residues, or at least the ones I've tried weren't.
FCS Harmony Racing
Momma always told me not to look into the eyes of the sun.
"But momma, that's where the fun is!"
The citric acid reacts with the top molecular layer of the Aluminium removing any oxidation.
One can use any acid, but the trouble with stronger acids like H2SO4 (battery acid) and HCL they are extremely reactive with aluminuim and corrode the surface way too deep.
After several attempts over the years to make aluminum intakes look new again and keep them looking that way, I finally figured it out. I painted it black. It looks good, plus I don't drive too much with the hood up.