I've got an old mopar 318 block. When I pulled the freeze plugs, the block was full of mud/sand/crap. I've cleaned it out best I can.(pressure washed, dug out as much as I can ) (by the way this is a bare block on the stand) I seen an old post about using Oxalic acid to remove rust. My question is/ if I install my freeze plugs, then pour the Oxalic acid into the water jacket ports through the head gasket deck holes. Will it cause any damage to the New freeze plugs ? Will I have to replace all the freeze plugs again ? Also how long should I leave the acid in the block ? Do I have to neturlize the acid afterwards ? What about using CLR rust cleaner ?