This is my first time getting any bend at all on a grade 5 bolt. The primary reason I didn’t get a full bend was that I didn’t quite know how to most efficiently crush down. Lesson learned.
Here are three spool valve engines. The one in the back is a direct implementation of mrpete’s single-acting spool valve engine using the excellent(!) drawings provided by toly@sysmatrix.net. If you ask for mrpete’s spool valve drawings, he will e-mail them to you.
The two in the foreground are also derived from the same source. Obviously, I liked the square head with eight head bolts better than the original round head. I also eliminated the spacer on the main shaft that positions the eccentric by doubling the thickness of the upright and machining the main bearing such that it is also a thrust bearing for both the flywheel and the eccentric. I like the thicker pedestal better, but that is subjective.