Winter Storage Of Locomotives

Attn: "Chuffer"
You asked 2 questions in response to my posting:-.
"..... finally being finished in 2012 would GM castings in those days be better quality or were you just plain unlucky? What process took place to seal the porosity in the GM cylinders and did it last? "

One of them made me realise I'd been unclear yet again.

I don't know if GM castings were worse in terms of porosity in past years. Those very porous castings I purchased must have dated from the late 1970s. I don't know from where the original purchaser acquired them, but from his location I suspect they were "from a M.E. supplier" in the north. I had no original receipt so returning them wasn't an option.. Of course many hours of machining had been completed when the porosity was first identified, so no-cost, GM replacements weren't my priority !
As to your question about the process & cost to seal the leaky castings ~ apologies, I wasn't clear.
I made a call to a specialist company to ask the cost for sealing the 3 cylinder blocks. Their reply effectively eliminated any prospect of going that route ! It was then I purchased the CI castings & Meehanite and started all over again.
The industrial process for sealing (using a methacrylate resin) didn't commend itself to me for use in a steam loco. The maximum operating temp for castings so sealed was quoted at 200 C. One company provides a reasonable description of the process involved (See their 'FAQS' tab on the website) :-
**LINK**

No doubt someone can provide more information about the longevity of the sealing or perhaps of different industrial sealing methods.

when I worked in high vacuum field, all ally forgings were sealed by putting them in an evacuated chamber and letting them outgas for a bit, then a bucket of resin, was posted in through an airlock and the forgings immersed, then let the air in slowly, fish them out and let it harden. I doubt the resin would stand steam temperature. This is all a long time ago, so might be not quite right

I've had just as much trouble with iron castings as with gunmetal with porosity. I put a thin sleeve made from cored bronze in my latest, although I doubt they would have leaked like Furious Fowler's, just a bit of porosity at one end of the bore spoiling the finish