WJPearce, I want to know what you think seeing as you are a fountain of knowledge on engines.
Thank you for the kind words camman, but I can only admit to being an amateur enthusiast. Still, I will outline my best guess below.
Most engines have a certain amount of overlap, where both intake and exhaust valves are open. While this is nice to help push out all the exhaust gases, it also lets fuel flow out the exhaust without ever being burned. With port or cylinder fuel injected engines, the overlap can be increased because only air is coming through the intake valves, not fuel.
The info jerryw posted came from Manuel Lage's book "Hispano Suiza in Aeronautics." The book was originally written in Spanish, then translated to English. Something could have been lost in the translation. The book states the air only intake valve opened 65 degrees before and closed 82 degrees after the air/fuel intake valve.
Below is the valve timing for the M-105/VK-105 engine from your post about valve timing.
Klimov M-105 (@0.078")
Int. open 10 deg. before TDC
Int. close 60 deg. after BDC
Int. duration: 250 deg.
Exh. open 60 deg. before BDC
Exh. close 20 deg. after TDC
Exh. duration: 260 deg.
Overlap: 30 deg.
Lift: 13mm (.511 in)
LSA: 112.5 deg.
ICL: 115 deg.
This engine has a 30 degree overlap. Many fuel injected engines on your list have an overlap of 110 degrees or so.
The VK-107+ engines are acting a bit like a fuel injected engine. Adding 65 degrees to the 30 degree overlap would give 95 degrees of overlap. I think that is reasonable considering that it is just air entering the cylinder.
The intake duration is listed as 250 degrees for the M-105. Taking that and adding 65 plus 82 would give a duration of 397 degrees for the air only valve on the VK-107+ engines. That seems a little ridiculous to me, and I do not know why one would want the air valve to close 82 degrees after the other intake valve.
I think the air/fuel valve could have opened for less than 250 degrees, since it could be a very fuel-rich mixture. Since these engines had 1100+ mm Hg (21+ psi / 73+ inHg) of boost, it would not take long to charge the cylinder. But I still don't understand why it would close 82 degrees after the other intake valve.
Here is where things fall apart. Could it be a typo? Maybe 28 degrees rather than 82? Could it be that the air valve opens 65 degrees before the other intake valve and 82 degrees before the EXHAUST valves CLOSE? It would have an 82 degree overlap while the air/fuel valve would have only 17 degrees. That seems reasonable to me.
Sadly, we can come up with a bunch of different plausible scenarios and be no closer to reality.
What I think I see in the pictures is an air valve that opens significantly sooner that the air/fuel valve. The air/fuel lobe appears to have a relatively sharp point, while the air only lobe is very blunt. So, the air/fuel valve has a much shorter duration of being open than the air only valve. But the closing of the intake valves seems pretty close. The exhaust lobe also appears to be less sharp than the air/fuel valve.
I think the air only valve could have opened 65 degrees before the air/fuel intake valve. I think the air/fuel intake valve might have had an open duration of less than 250 degrees (but maybe not). I think the air valve closed after the air/fuel valve, but only by a little (maybe 28 degrees).
I have labeled the close up pictures of the VK-107 valve train. Look at the lobe difference between the air and air/fuel lobes. Look at how they appear to close about the same time. Compare the size of the exhaust lobe to the air and air/fuel lobes.
Of course, all this is speculative based on some grainy images and something written about a Soviet engine in Spanish then translated to English. We might need to go to Russia to figure this out.