[chuckbrandt]

The gist of the drillbit test is that the bores on an FE are (I believe) 4.62" apart. So if you take :

(4.62 - your bore - your selected drillbit) / 2 you will get your average cylinder wall thickness at that point.

Bear in mind this isn't a conclusive test because it only measures the bore at one point and not even a very critical point, but it can give you an indication.

You will probably get many answers as to how much is enough. I would evaluate the thickness in the major thrust after you do whatever you expect to do to it for boring. (IMHO) I would want to see 0.120 in the major thrust direction (the outboard side of the right cylinder bank and the inboard side of the left cylinder bank). If the drillbit test suggests about that or more I'd probably go for the sonic test.

Chuck