Having spent a long weekend in a caustic bath the heads returned in a slightly cleaner condition. Some paint was even too stubborn for the bath and had to be removed with paint stripper and emery cloth. All passage ways have now been washed out with water.
Cylinder head stud holes were cleared out with an 8.5mm drill to remove any remnants of corrosion, paint, dirt and gasket sealant. NOTE that the upper 1/8" of each hole had been compressed by the head nuts and required a small amount of metal removing to get back to the correct diameter.
The four oilways feeding the rocker shafts were cleaned out with 1/4" drill; these were still full of solidified oil.
'A' head, centre row, #2 stud hole was repaired with ProWeld resin to remove the small grooves that had been drilled along side the stud when removing the head.
Before continuing with further work the gaskets were tested for damage following their immersion in the caustic tank. Using rubber strip and plastic cable ties the heater tap and temperature sensor holes were blanked off. The front end-plates have 2 holes tapped in them for the HT cable brackets; these were sealed off using duct tape. A stout board (3'x1'x1") was used as a base, covered with a thin sheet of foam rubber and topped with cling film. The head was placed on top of the film and someone stood on the head to seal the bottom water holes. The heads were then filled with water through the outlet pipes and the water jacket and end plate gaskets were checked for leaks. Although not under pressure this test does at least prove that there are no open breaches in the joints.