Corrosion behind core plugs

In the process of stripping a 200 to rebuild it prior to bunging it into my 90. Just removed the core plugs, and there seems to be a lot of corrosion inside.

The engine is out of a crashed Disco, and I think it was removed a while ago, partially stripped and left for a time. The areas above the remaining antifreeze level has therefore corroded.

I'm concerned about all this crap floating around in the cooling system, but there is no way to mechanically remove the rust.

Has anyone any suggestions, perhaps some sort of rust conversion liquid - main problem is the volume, and therefore the cost.

Photos hopefully attached.

I used Kilrock large appliance descaler in my old series rad to get all the crap out, did a good job.
Got it from robert dyas.


Lynall

Thanks for the reply Lynall. I think I will have to use some form of acid, don't think that there is anything in the block which will be hurt.

no there isnt its just a solid block ,its not that bad, i just steam clean them out making sure bottom of block were it would sediment up is thoroughly flushed out

[FONT=Tahoma, sans-serif]An update, as someone might have the same problem in the future.[/FONT]


[FONT=Tahoma, sans-serif]I power washed the internals as best I could, through the core plug holes. I turned the casting over so that bits could run out through the holes.[/FONT]


[FONT=Tahoma, sans-serif]I then replaced the old core plugs, with grease around the rim to act as a sealent and ease their removal later. I put the casting as level as I could, and bolted a bit of wood with a plastic seal behind, over the water pump, shown in the port plug photo. I used an engine mounting frame, which made life much easier.[/FONT]


[FONT=Tahoma, sans-serif]WARNING! Sulphuric acid at any strength is dangerous. At 91% it will burn a hole in you before you could wash it off, and any contact with an eye will give you the fashionable Pirates of the Caribbean look. Both eyes and you will have to use the Braille version of this forum. Use strong plastic gloves, the tough version of Marigolds is OK, and a full face shield or chemical (NOT normal) goggles. Wellies will keep your Gucci loafers from melting.[/FONT]


[FONT=Tahoma, sans-serif]I poured 1 1/2 litres of water into the casting, then followed it with 500ml of 91% sulphuric acid, sold as drain cleaner. Always add acid into water – water added to sulphuric will instantly boil, spitting out sulphuric drops like a frying pan with bacon. Topped the casting up until it was as full as possible, and left it for four hours. Drained the acid out into a large plastic box, and tipped it into the drain, and with a hose rinsed the unit, making sure the bits inside were flushed out.[/FONT]


[FONT=Tahoma, sans-serif]Simples, but I take absolutely no responsibility for anyone damaging themselves or anything else with the acid. [/FONT]