You appear to be willing to try just about anything.
You may or can try a thermal imaging system.
Can't help you on who or where, but a PM380 or better camera will allow you to record on video tape the engine from cold to hot.
You might be amazed at what you find.
If you can find a person in your area that will video it for you, have it stored on video tape. then you can go back and look at the engine in time.
I use one on an engine once to find that there was a chunk of metal in a cylinder head. I don't have access to the camera any more.
Just my $0.02
