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Walter -- That enamel was there to do two things: 1) capture any residual chunks of the casting cores that may have hidden in the nooks and crannies inside the casting, and 2) seal any porous areas of the casting. Both of those purposes are worthwhile, and I would suggest you repaint the interior of your castings. As has already been mentioned, Glyptal is somewhat of a de-facto standard that has taken on darn-near mythological status. Glyptal used to be a General Electric product (GE "spun off" the Glyptal line quite a few years ago) that was fundamentally intended to be a paint-on electrical insulation that would hold up inside oil-filled transformers. The generic term describing Glyptal is "red insulating varnish", and I believe that most of the major paintmakers offer a comparable product. There is, other than the price, one downside to using a red insulating varnish inside a casting . . . it's DARK in there. From what I've seen, just about any oilproof enamel will capture the cooties and seal the pores. (at the same time, I'd personally stay away from latex-based enamels) I've used mis-mixed oil-based enamel from a local hardware store, which they sold for about US$ 1 a quart. Using a light color -- light yellow, beige, ivory, mint green, and so on -- made it a lot easier to see what I was doing inside the casting when I was doing the assembly work. A former co-worker of mine used a catalytic-cured enamel sold to refinish bathtubs on both the inside and outside of his boat's engine block. He seemed to like the results a whole lot; it made the engine compartment much brighter and any seepage was very easy to spot but wiped CLEAN with a dry rag. John
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Rod