I took cylinder heads off for some maintenance, grinding valves among others to improve compression. I tested the valve seals by pouring isopropyl alcohol in intake and exhaust cavities and waiting 12-24 hrs to make sure the leakage through the seals was minimal or nonexistent. I have no reason to suspect that piston rings are leaking because the leaks of 20-30% before I took the heads off were consistent with the state in which the valves were and which I serviced, however, I would like to test them anyway because the heads are off as they too can cause cylinder leakdown (as well as bad head gasket). The remainder alcohol in the chambers I can easily suck out with a syringe. Assuming that any alcohol leaked down past the piston rings into the oil pan will drain through the oil drain, do you think this is a reasonable method for testing piston rings?
Piston rings don’t seal perfectly due to the fact that they have a split in them, so there will be a tiny gap where alcohol will leak past.
When piston rings are fitted, the splits are placed 180 degrees away from each other on adjacent rings to restrict the flow of gasses, but some still gets passed.
Engines have a PCV system to deal with these gasses.
I don't think this is a reasonable method.
To assess a test result, you'd have to know how a healthy set of seals would behave under the same test conditions. Do you have other test results (using this isopropyl alcohol method at room temperature on known-healthy valve seals) to compare?
If test results using isopropyl alcohol on known-healthy valve seals are not available, what evidence supports your assumption that valve seals will behave similarly with room-temperature alcohol as they do with higher-temperature oil as found in a running IC motor?