Well, that was interesting! Thanks for locating the video, Pat. They did quite a few things that seem non-ideal to me. But if it is working for car guys....
1. When you spin at such a low rpm, you do not get anything like the inertial forces acting on any of the moving parts that you would during actual running. For example, running at 10,000 rpm would increase the force on the rod by a factor over 100. The wear pattern will be different due to dynamic distortions that are likely. So the break-in isn't really done, but it may be started. It seems that the entire focus is on the pinch at the top of the stroke. That makes perfect sense.
2. Running without the backplate seems pretty questionable. In the mode they are operating, there won't be much load on the piston, so the effect is reduced, but the big end of the rod could start walking south with gravity, tending to wear the lower bush at the edges.
3. The temperature they are achieving seems a bit of a mystery. They didn't talk about whether the engine was fully immersed, but if it is (and you avoid stalling the motor from hydrolock) then with the very high heat transfer rate possible with liquid contact, the whole engine will track the bath temp.
4. I wonder if the change in the noise at just below 900 rpm is when the engine is now going fast enough that the oil will not significantly re-enter the cylinder between cycles. If so, I can see why they would not want to run it just below this speed, as the loads and forces might be fairly high as you try to pump oil instead of a vapor bubble, again assuming the engine is fully immersed.
5. The only thing that seems sure about this method is that your engine won't suffer from a paucity of lubrication at any time. By the way, flooding ball bearings during operation actually raises the temperature of them higher than they would see if they had a normal lubrication level. Since we assume the bearings are highly coupled to a controlled bath temp, that's not an issue with this setup. But it is a reminder to guys that think that running sealed bearings heavily loaded with grease "for long life" may not get you what you are looking for.
6. Having an exposed wing nut style knob on the top of the unit is a safety issue in my mind. But the interlock switch is thoughtful. However, the switch actuator should have been recessed so that no one can easily put their finger over it to defeat the system just like he did in the video. Yeah, I've been around the tree a few times with the product liability lawyers...with little to show for it but a few more dead brain cells that they passed on to me.
7. I'd throw a samarium cobalt magnet in the bottom of the tank to scavenge any steel swarf and wear particles. If I owned one of these.
The approach is obviously a creative answer to a perceived problem. If it is working for them, then it's all good. I am a bit puzzled though, because I have run a few car engines on racing planes and never seemed to have any break-in issues. These were mostly OS engines, if that makes a difference to guys that know cars and truggies, although I did run a few others.
I think this process would actually help an Enya .09 more than an OS car engine, for what that's worth....
Divot McSlow