Ah, now I get it, they are speaking of the springiness of the piston rings or pressure against the cylinder walls. I must confess that in all my years of engine work, I have never made such a test or even know how, other than “looks good” or “feels good”. I’ve seen a wide variation of “normal” though. The skinny pressure-back rings are very weak. On the other hand, I’ve seen rings for industrial four-stroke engines that had so much tension that they were very difficult to get into the cylinders.
