Originally Posted by
DmaxMaverick
Also, boring a 6.2L red block to 6.5L bore diameter isn't advisable. There was only a short run of 6.2L blocks that would be a candidate for that, and they were limited to 1991-1992 castings (as I recall, the crossover years between 6.2 and 6.5). The same block casting was used for the (soon to be obsolete) 6.2L before the introduction of the 6.5L. Again, the engineers are way ahead of you. The maximum recommended bore diameters ensure a margin of practicality, and considers most/all contingencies, such as core-shift and metallurgic deficiencies. Of course, there are "perfect" blocks out there, but who's to know which, or even how to identify them? The block you're considering at the moment is already defective, for reasons unknown.