IIRC, I think the company I was researching was something called Tekvac or soemthing like that. Had HCPIIP and PVD application processes, which I think would work for an engine bore(in theory in my head at least???). Essentially turn the cylinder itself into a vacuum chamber, as long as you could cap the bore on both ends perfectly. I guess the real trick with the HCPIIP application would be getting the cathode to be the cylinder wall. Anode(s) could just be the plugs.
Ah so many things. So little funding :lol