Ive done a few and I normally bolt in nylon plugs under caps to protect Journals. I like to be careful though... For the lifter bores I slide in plugs also. Im sure you could use some sort of barrier cream, that caustic wont eat too...(cant think of any) Im not going to say if dipping unprotected would effect things, I doubt it would really, but Im not saying either way. For nitric de-smut ALL steel items must be removed. Dont forget the spring perches, they can stick there un noticed sometimes.
Cheers, i've got a spare cylinder head and the g/f works as a chemistry researcher so i'll give it a go!
Holy thread resurrection Batman! Having cheerfully bought the scabbiest engine mounts in the land I went to buy some nitric acid, nope not going to happen. Turns out that it can be used to make explosives, and as such can't be bought by plebs like me. So, do we have any chemists in our midst who can suggest alternative chemicals to remove the smut from the alloy?
Where's the fun in that? Although it would sort out the issue. In the meantime I've bought a cheapo soda blasting gun, see if it's any use at the weekend.
Red diesel? cheap and reasonable for cleaning, also good for painting sheds, modern creocote doesn't quite cut it for me.
I'm very lucky, my wife when we went on our first date at the science museum in Manchester told me she loves the smell of oil and old things, so ticked the boxes
I've used RaceGlaze AluBright with some success on mucky inlet manifolds. AluBright Deoxidiser (500ml) RG71-500 (raceglaze.co.uk)