How do you get your used parts so clean?

Greasy bolts, I soak for a few days in a closed container of mineral spirits, let them air dry on a paper towel, then rinse them with brake cleaner.

Carburetors, I boil them in a crock pot with a mixture of simple green and water.

Aluminum intakes I will bead blast.

Other metal parts I will just sandblast.

I am going to dip a rusty 340 block I have in a 55 gallon barrel of feed grade molasses and water this spring, as soon as I can find a plastic barrel reasonable.