At the bottom of the barrel there’s a spigot, which has a location protrusion. Rather than machine the top of the cases as originally planned,, Bob suggested we make a compression plate to fit, keeping the cases flat at the top. I like this idea as by skimming the plate, or making a few of various thicknesses, we can alter the compression ratio.

The original Hercules is only 7:1 as it was supercharged. This engine won’t be (at first 😉) but should run ok. With a sleeve valve engine, higher compression interferes with the valve opening times. The piston effectively gets in the way of the ports, much like with 2 strokes. Next job is to make the plate, so we can get on with marking & drilling the cases.