phosphoric cleaner

[rx jamie]

im considering cleaning some grimey engine bits, especially the sooted up rotors. i will be using a phosphoric acid solution around 5% most likely or less.
 i know through my job that phosphoric is excellent at cutting through organics. i\'d just like to know what sort of metals can be found on the inside of a 13b.
the front and rear housings seem to be aluminium alloy which is fine. but the end plates are cast i think so they are a no go. what are the rotors and bearings made from ?
just for piece of mind really. i dont what my engine bubbling out of spec.
cheers