Today I finished repairs on the lathe that I started last week, and began machining up the new engine.  

I managed to finish most of the inside of the engine really quickly with the help of a 25mm (same size as the internal small post combustion chamber) drill bit I picked up this morning. We changed the design back to a straight convergence/divergence for this prototype. It is possible to do the curve by hand by roughly stepping the shape by hand and then sanding by hand but its quite time consuming.