I'm not sure there's a single place that where you learn everything. I picked stuff up here and there from lots of different places, peoples, things, books, etc. The rest I kinda learn on my own by working the math, doing it on my own, and trial & error. It's probably better that way so that you don't get overwhelmed with information all at once and you can put the pieces together on your own.

I'd say start with the terminology and basic principles. For example, piston-to-deck height clearance, compression height, deck height, rod-stroke ratio, lift & duration, dwell, dial bore gauge, micrometer, ABDC closing, static & dynamic compression ratio, surface finish (Ra, Rz, Rk, etc.), dgree wheel, cam spec sheet, rocker arm ratio, spring install height....man I could go on forever. That's not even touching materials, material properties, and material procesing. You damn near have to be an engineer to know much of anything useful.