I’m not sure if I’m the only one thinking about that but how about compression ratio start at 2:1 instead of 6:1 ?? It would be more easy to make an old/early-day engine without having to flood it with fuel, using extreme cam profiles and almost dead timings for ignition… not a big request I believe, hope it can be taken into the game someday.
Never had problems with that, so it seems a bit of a weird request. Even with 80 RON fuel you never need lower than 6:1, given modest timings. Are you maybe being a bit aggressive on some of the other sliders?
Maybe, I tend to leave compression last when adjusting an engine. But still, is that possible to be made?
Even the old Ford Model T 4 cyl sidevalve engine had 4.5:1 comp ratio. Thats in 1908. The game starts 37 years later.
I’m not sure if such car had any kind of timing advance in the ignition though. O.o’’
When making an engine, you best start out by setting compression low and then go from there, not the other way around 
lol thats exactly what i do, the first thing is set the compression all the way down and work over the cam profile, spark timing and AFR, my idea is always to keep the AFR 15:1 and advance the spark timing as high as possible, thats when the low compression would be useful… lets say for example, in the worst case possible… trying to run an engine made in 1960, with the biggest bore possible, push rod header, and only 1 single barrel carb, all that with 80 gas… such engine would need to run with 0 spark advance, 13,4:1 of AFR and then maybe with a 80’ish cam profile(that is totally not efficient in a wide bore engine), in those conditions it would run… poorly, but still it would not auto destruct on the first start… but then, just by having lower compression ratios all this situation could be avoided, giving the engine more power, efficiency, response and it would not look like a steam train with all the smoke… lol
Well wait, you’re maxing out the bore size then running it through a single barrel carb? What color is it on the engine display? If you have parts of the engine turning red or orange you’re restricting air flow and costing yourself octane. (Except of course pistons, rods and valves)
Intake, header and exhaust headers are all green, the only red thing are the valves, but still even if the engine is about to spit the valves out, the air flow seems perfect. (adding one extra single carb does not change much, 1,5hp in more than 70)
I do not know 100% how it works in real life, but in automation the best combination of Ignition timing and Compression tends to be a compromise of both.
Also, to add to what nialloftara said, there are a few things that are very unoptimal for 80 Ron fuel. Very Oversquare engines tend to require higher octane ratings in the game, same thing for OHV vs OHC.
There is also the single barrel carb issue. While there is the issue with choking the engine that nialloftara pointed out, the carburetors with less barrels tend to require higher fuel octane.
In 1886 the Mercedes Patent Motorwagen 1 engine had a 2.7:1 compression and you want 2.0:1 as lowest 
The game starts in 1945 not 1845.
Just lower the ignition timings and give the engine a bit more fuel, its actually very easy. The first car after the 2nd World War from Mercedes utilised an engine with a 6.5:1 - the later developed M121 engine already had a 8.0:1.
Before you complain do reasearch in real-life engines and if you want to run a giantic 1960 engine with 80Ron, and throw in Pushrods and a single barrel carb then its pretty obvious that you will hardly be able to make it work.