Don't see these being a factor at all even at moderate power levels. Just because you have 4-bolts per head, doesn't automatically qualify it as a weak link. You have to factor in not only casting materials (head and block) but types or grades of metals as well. We all know this engine has a compacted graphite iron block which is incredibly strong compared to that of a traditional cast iron block because of increased density and rigidity at a molecular level. Couple that with high tensile strength head bolts and high grade aluminum head castings, you have as robust package. Now add the fact that this engine was designed for commercial applications i.e. buses and chassis vehicles including RV's...you know that this was designed with severe duty fleet use in mind...hence the ISV, which is the single variable vane turbo model of this platform. Cummins had this engine underway back in 2006, it's had some pretty extensive run time before it's made it in to the titan xd. The only unknowns are associated with the air charge system, but knowing holset, they are pretty good about turning out decent products. So rest easyWe all know how the ford 6.0l diesel was with 4 head bolts per cylinder. Does anyone see that being a factor in these 5.0l ? If no what is the difference?