There is ages-old method of estimating depth of pitts and determining which pitts are especially deep. It can be called "oil-film" method. It consists of spraying oil down bores and letting it flow out to more or less uniform layer. One can immediately see where deeper pitts are because surface tension of oil will not be enough to maintain flat surface on oil film. Instead, deeper pitts will be seen as depressions.
Attempts to estimate thickness of oil films can follow any method you have access to for measurement of film thicknesses, either directly or indirectly (say, on surrogate metal surface).
Would never suggest this is replacement for good meassurement of wall thickness or bore scope, but, it can sure give some usefull apprasals of pitts in bores.
Niklas
