These are old glow motors! They do not run on gasoline rather a mixture of methanol, nitromethane and various kinds of oils (primarily castor and different types of synthetics) and achieve ignition with a glow plug, which is basically just a piece of platinum alloy wire that gets heated orange-white hot (hence the glow name) I believe these engine sizes are .20 and .40 cubic inches as you stated - usually on OS engines the displacement is on the casting somewhere.
These look like they may have not been run, or if they were it wasn't for very long. I doubt they're broken in fully yet. Since they are I think ABC engines (some early FP were ringed but I think this was only ever 40 size and above) when you do go to break it in, be sure the cylinder can reach operational temperature and properly "bed" in with the piston. ABC engines achieve good compression by having the cylinder wall be slightly tapered - this is why when you turn it over when it's cold (you shouldn't actually do this) it will have some "pinch" at top dead center. When at proper operating temperatures the top of the cylinder will expand and assume a less tapered shape.
What's sure here is you have some good motors. I have used many, many, many OS 2-strokes in my planes, LA, AX, FX, FSR and more, and I still consider the FP series superior to all. In fact, I think OS engines from the 80's are better than anything they make today. Treat them well, always run a couple clicks rich, be religious with the after run oil, and you could put a tank or two through them every day until you die and they'd still run good as new.
Another side note for me: I have a 25 FP that also came with an extended muffler with an extra baffle like the 40 FP here. Didn't know they made them for other engines!