I was fortunate enough to be raised by a Chrysler master tech who was raised by a Chrysler master tech. Much of my knowledge just kind of trickled down from them, because I really didn't have an interest in automotives until I was around sixteen or so.
I mostly expanded my knowledge by looking into vehicles I had an interest in and researching what made them special over other cars. I remember one of my first pursuits being a Dodge Neon SRT-4, which featured a turbocharged four cylinder dual overhead cam engine. I pretty much had no clue what any of that was, so I looked into it. Even then, I didn't really even know what a cam was, I just knew it had two while less performance-oriented cars had one. I focused on what I could grasp: cylinders. I learned their layout is what made a V6 a V6 and a V8 a V8, or an inline four, or an opposed four, and so forth.
Once I understood varying styles of cylindrical formatting, I focused on what they did. Cool, they control detonations that stroke the piston up and down to create power. Then I could focus on the turbocharger. Cool, it increases the air density inside each cylinder to maximize the potential for fuel combustion. Then I started looking into the crank, cam shafts, rocker arms, distrubtors - each concept building and expanding upon the last.
I wouldn't say there is or will be any single source of knowledge, unless you really are the reading type who can buy a book and implement it systematically. I relied mainly on articles like those found on Wikipedia, but I will say about a year ago I purchased a book titled
The Reader Digest's Complete Car Care Manual. It was published in 1981, which may seem outdated, but really isn't. I like it because that year really represents a shift of engineering for the automotive field - computers were growing increasingly smaller and mechanical efficiency was being optimized using these systems. Much of the technology we use today simply could not work without varying degrees of computational devices. So you get this kind of timeless view on the fundamentals of automechanics versus the conceptual goals of how automotives could be. It was very exciting to see how the most advanced technologies of then are are now features expected to be equipped in any new automobile, but I'm beginning to stray... This book really is an end-all be-all for someone desiring to expand their knowledge on all aspects of a car.
Anyways, I love cars

I suggest finding a car you can grow attached to and devour any information there is to be had about what makes it tick. Have fun with your research.