[K.Wilson]

Chris,
I tried to get this to post before but it would not post so I will try again.
There have been a few threads in the past on this topic, but here are the basics:
Take the shank of a drill bit (not the drill end) and slide it between the cylinders thru a freeze plug hole. Find the largest size bit that will go in and measure the diameter of the bit. Then take a caliper and measuer the distance between the same two cylinders at the top of the block (this assumes there is no "ridge" at the top of the cylinders). Measure it several times and use the smallest number, then subtract the drill diameter and divide by two and you will have the cylinder wall thickness.
Web thickness minus drill diameter divided by 2 equals wall thickness.
This is only true if there is no core shift and it assumes that the cylinders were bored in the center of the casting.
I my opinion this test should only be used to see if the block is worth spending the money for a sonic check. In other words it can prove the block is not usable and save the cost of the sonic check but it should not be used to prove the block is usable.
Keith