[dtw]

The most important thing that's missing from what you listed is key for the mag cased engines, especially the 2.7s. The main bore must be measured for straightness/roundness. An offset bore can be detected which is the telltale of a case that's been twisting around the crank (walking, which is what shuffle-pinning is designed to stop).

I've had two mag cases redone now. One was out of round, which means the main bearings wore out and the crank began to pound the case oblong/out of round. My other one was round but offset, showing that the case had twisted. In both cases I got lucky and the total movement was limited to 0.001". A very light align-bore plunge fixed things up just fine, and I was able to run standard bearings in both cases.

Tim just had an example of a case that was so twisted (0.006"), it could not be repaired without expensive surgery, involving facing down both mating surfaces of the case halves and then reboring the mains. He found another good case instead.

If your case was tweaked and it was just slapped back together with new bearings, the bearings will bind up the crank where the case is twisted. That's why I would recommend replacing them if you find out that the case/crank is the problem. They've had serious stresses applied to them that they weren't designed for.

Another possibility is that your rings froze up in the bores, but I'm having trouble thinking that's the problem - the time frame you discussed isn't enough time for brand-new rings with at least a little bit of lube to become completely frozen.