Thanks Bent. The change of plan (the brass fixing bits) means that the JB Weld is no longer needed. But I do think it would have been OK, given expected usage, i.e., yes, probably short runs, and the positioning near the bottom of the cylinder. As far as the shrink tubing goes, I'll find out when I get there. The worst that can happen is that it shrinks up tight and is hard to take apart, in which case I can cut it. The way it stands now, I can easily remove both "coolant pipes" for running if desired. The engine is actually air-cooled, and either a prop or a fan will probably be used to help with that. I had ideas for making the coolant loop functional, but at this size it looked like it would be more trouble than it was worth.