When you look at the block it is obvious that there is less material in the front of the block which seems to me like the major reason for failure to me, but there may be something else that also is slight contributor....heat. If we assume (which I am sure this isn't always the case) the injectors flow the same amount of fuel to each cylinder, the front cylinders would run slightly cooler than the rest because they are getting more air (especially if you don't have a ported intake manny). The hottest areas would be between cyl. 2 and 3 and 3 and 4. In theory, since cylinder 1 would be running the coolest, the expansion would be less there compared to cyl 2,3, and 4. I would think that would put more strain on the front studs cause the rest of the cylinders would expand more than cylinder 1 so there would be more force generated at WOT to lift the heads from the block on cylinder 1. That would be made worse by over torquing the studs. If this is a factor, that would make yet another case to run a ported intake manny....of course, I could just be FOS.