Thanks everyone for all the advice and help.
I've found some of the evaporust stuff (called Thermocure).on ebay. Will give it a go.
Will give the block a good flush back and forth, then will add the Thermocure, run for a few days and flush again.
Think I'll skip the filter - I fear it may block with time and reduce water flow?
"Y mae dafad ddu ym mhob praidd"
1972 4/4, 1981 MGBGT, 1984 FLHT1340, 1980 XLH1000, 1990 ZX10
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