I used the big 5 gallon ChemDip, full strength. You will need to turn them over to get the whole manifold covered. Afterwards they were clean but somewhat mottled in appearance. So I bought a cheap tractor supply blasting cabinet and glass-beaded them to a beautiful satin finish. Now I just try to avoid touching them they are so pretty.So the harbor freight cleaner says don't use on aluminium. Did you dilute it at all or use it full strength?