By chance are the limits we can have going to be pushed any? For example, the current revision of my engine (a 192 cubic inch naturally apirated I4 with an air filter, a catalytic converter, and mufflers) is making 613 horsepower. And I’m happy about that, but when you look at the statistics it’s fully obvious that it could be much better. It has the full bore, full stroke, full cam profile, fully retarded valve timing, richest AF mixture, fully advanced ignition timing, 12,000 RPM redline, and uses 100 octane fuel. It’s at 14.6:1 compression, but if I go to 14.7 it will detonate. If I lower any of these extremes, I lose power, so that means that I don’t have room to get the full potential and best balance of all the factors out of my engine. I’ve found that retarding ignition timing to raise compression lowers power, so I would like to advance timing more and lower the compression more, or just use higher octane fuel altogether. I figure in reality if I go out to my van and turn the distributor cap all the way, I can advance it as much as I want, until it not only loses power, but sputters and backfires and just won’t start, so why not factor that into the game? Let us richen the engine until it floods, retard the valve timing until practically no air enters the engine at idle (and maybe even let us set a high idle to counter it), let us run a big enough cam that the valves will hit the pistons, let us run high enough RPM to blow up even the stoutest, least powerful engine we can build, and let us raise the compression to, say, 20:1! Why not? I think there should be more risk, and more room to improve. By the way, how big can the bore and stroke get on the V8s in the actual game? I would love to build a 632 big block (4.6" bore, 4.75" stroke).
Valid points fordman. There is a simple reason for not going (much) more extreme than we do already (N/A I4 with 600hp? hello? 
) - playability and intent.
Playability: having it like you describe will make building normal (usable) engines more difficult as you get more useless choices.
Intent: Automation is not a “Build-Wacky-Useless-Engines Tycoon Game”
V8s will go to about 12L in capacity 
Cheers!
How is a 12l V8 not a wacky useless engine 
? (well, except in Tatra trucks where they are awesome)
But just because of this, I’m gonna build a kei car in the first version of Automation and then make a revision and put a 12L V8 in it. And I’m gonna call it the Keizilla.
Aw, man, 12L is only a 732! I’m assuming bore-spacing is one of those variables that will adjust itself, rather than requiring us to start from a certain block configuration.
AND we should be able to build F1 engines. V8 and 20k RPM, what could be better?
The “problem” with modern F1 engines is that their valves work entirely different, and that system is basically only used there… so a lot of work for more or less irrelevant content for the world markets which we aim to simulate. That’s sad of course, because those engines are awesome 
but nothing we can do about it for now.