Id kinda agree with Chris, Ive checked quite a few blocks and haven't been that lucky with wall thickness, on my last engine build I didn't find one with that good of numbers out of 10 blocks checked, makes me wonder if my checker is bad?
I try to alwyas calibrate my sonic tester to a known thickness, not the posted velocity for the metal being tested
I'll take a dremel tool or small hand held air powered high speed rotary grinder with a carbide bit to smooth out around the oil pan rail on the BB in the back near the bellhousing mounting starter areas or in the front near the timing cover ribs to get a smooth, flat surface
I measure it with a set of dial calipers and get the meter reading within .005 or less on the meter
