[quote:de02298d24]I have sonic tested about 10 blocks, and found wall thickness (4 points measured around each bore) varying from 2.8mm (112 thou) to 5mm (200 thou). Maximum core shift in any one bore was 2.8mm min to 4.7mm max - a B234F block, not my favorite, I use B230 blocks from '89 exclusively now. The best I measured was a B21 standard bore with 3.9mm min, 4.9mm max over the 4 pots. [/quote:de02298d24]
Ok, sounds good, especially that you've proven to your satisfaction that the walls aren't actually that troublesome. I'm still surprised that my two blocks are the worst out there- just seems my luck must be bad...??
My b23ft block, still sitting a few steps away, was bored .040 before sanity took over and I had it sonic checked. After boring, but before final honing, it had an area of .066 thickness. It can happen. I believe Calgary Richard recieved the pics I have of the aftermath of a Ford 2.3 breaking a wall. It's ugly... I also was in corespondence with another Canadian using Buick forged pistons, who cracked his bores. We went over every detail we could think of, and saw no assembly or other fault.
I think we can agree that the b21ft in std was the all time best for thickness. Just stands to reason. Volvo 'used to' cast some very thick walls- my 1963 b18 is .207 nominal over, and ran a supercharger for a summer, through a lot of tuning problems, and showed no problems. Still, my 'better' b23E/f NA block has the between cylinder area very consistently around .105, with the front cylinder too close to the front with a .104/.160 shifted bore. If I use this block overbored .040, I will have thickness somewhere in the low .080's
Sounds like the shop I am dealing with (they have several low 7 second cars) and Richard Prince agree that .110 would be the minimum in general. I'm think bore the #1 moved so I only lose .005 at the front (down to .099-ish) and set the block at an angle facig down to the rear and use block fill up to about the half way point for #4 and up to the water pump hole for #1. then I can add N20 or an Eaton M90 in a few years without worry.