It ran, but lacked power etc.
Remove your hat before entering the operating theatre…
The broken intake runner wasn’t helping.
Improvised surface plate, and blobby brazing. There were many stages of brazing, so at this point, the aesthetic didn’t matter.
For old castings, I find that using an abrasive spot blaster cleans faster and deeper than grinding.
After many years of use, the manifolds and their mating surfaces were nowhere near true to one another. This is the heat exchange flange. Braze bead buttering is an amusing process.
Trueing the flanges. Build up, rough grind, (used a wheel designed for grinding aluminum. It doesn’t load up with non-ferrous metal), check for flat, then repeat.