Heat exchangers are pricey and it seemed like a good learning experience, so I tackled the heat exchanger as a multiple part project.
The part of the heat exchanger that connects to the engine exhaust was broken, which I suspect is one of the main causes of Ruby running at a max speed of 35mph. There is a flange that should have been connected to a pipe leading into the heat exchanger, but it had long broken off, even after someone's attempt to braze it back together.
This was a two day project, with half of it being grinding...Old cars get rusty let me tell you, and the bolts just don't want to come off...
1. Grind off the six bolts holding the heat exchanger in place.
2. Remove any additional attachments to the exhaust system.
3. Make a new flange (cut from a piece of 3/16" sheet metal, drill holes in corresponding locations).
4. Grind off the old welds.
5. Cut a new section of pipe.
6. Wire weld the new pipe in place, being careful with the varying wall thicknesses.
7. Weld the flange to the new pipe, making sure the pipe was at the correct length so the heat exchanger would fit back into the exhaust system.
8. Bolt heat exchanger back into place.