Thanks freebird. I reckon there is a good chance that it will work. In point of fact I came across a relative today who tells me he made his own manifold for a 2-stroke. He showed it to me - just a couple of old galvanized plumbing fittings threaded together and a bit of rolled tin. lol! Looks rough but the engine starts and runs well.
The epoxy stuff I used is called Pro-weld, which is a close cousin of JB Weld. Maybe not quite as heat tolerant, but I have used it in the past to repair broken heat fins off engine blocks and it has never shown any signs of melting or letting go. Very strong stuff! In one case I rebuilt the entire lost fin out of Pro-weld and 6 months on it is still there. I've also just been told that most epoxy welds are only flammable in the wet state. As soon as they set hard they lose most of their flammability. So when dry it is probably no more flammable than dry engine paint.
Still, I will be watching this manifold closely and maybe try a bit of fibreglass insulation if it looks like overheating. Will let you know if it works. :-)
