I think majority will agree with me that if you have to ask how to make an engine, you really shouldn't be making one. Those things aren't some kind of set in stone program that games must have to run properly. 3D engines are not trivial software and a lot of them go for big bucks because they are challenging to create properly even for seasoned professionals. If you're looking to create the engine for personal use, it would probably be best if you focused on making the game, and then another game reusing some code from the previous, perhaps make some tools to make the process more automated, etc. etc. and slowly, but surely, you will have yourself a capable engine flexible enough to handle very tough challenges with a few tweaks. Imagine this to be somewhat like playing the piano. You can certainly download the sheet music for one of Volodos's pieces but without the proper reflexes and coordination, you will never be able to play it. Without experience, you'll end up with a buggy bulk of code that won't be very capable nor versatile, and you'll get frustrated along the way (more so than if making an actual, specific game).

That's of course not to doubt your skills in programming or anything, it's just that making a functional engine is not an easy task, more so without the know-how in the first place.