I am after help again with this old engine of mine, does anyone know of any good chemical products for the removal of rust/scale build up, from the internal waterways of a cast iron cylinder head & block?
I worked with the fleet engineer on a River Dart grockle boat some years back. His problem, as well as the rust, was that the boat operated in shallow water and was raw-water cooled. He took off each head (1 per cyl - big beggars) and stuck it on a gas ring for half an hour. Once the gunge dried out he then chipped out any blockages in the waterways with the tang of a file.
I said you wouldn't want to hear it, but you did ask!
If you want to settle the rusting down whilst still using the engine then a spoonful of soluble oil (that milky stuff us machine shops use) in the coolant will stop rust and your engine water pump will like it.
I'll send you some if you would like to try!