Only problem with most optical pyrometers (laser temp guns??) that I can see. . you don't get a good reading of what's going on UP THERE while the plane is flying, by the time you land and taxi over the motor has had quite a few seconds (30-40) at low throttle during landing approach, and if you try to take the temperature with the cowl off the cooling airflow totally changes. Kind of a hard way to get an accurate measurement. Then, the ones most people buy make it hard to pick the hottest spots for their readings. Imagine the differences between the top of the head and the exhaust port area. Then, are you hitting the side of a cooling fin, the cylinder between the fins, perhaps someplace else?

As has already been stated, though, its very doubtful that the painted cylinders are being marginalized for cooling due to just the paint. I know that if I was an engine manufacturer I'd never do anything to make it harder to cool these things off. . There's already too many pitfalls and problems as it is.

I stand corrected (MILDLY) Diablo on the idea of "pores" versus "porosity". Every cast metal has some sort of porosity to it, it's the nature of the process, though some materials have a LOT bigger holes/voids than others. but. . "Clogging"?? uh. . . no