geordi wrote:
dirtmover wrote:
geordi wrote:
.....based on the observations that the factory torque between cylinders 2 and 3 are massively different (and less) from the bolts around them. This is from the factory and I am about 75% certain that this is why people are losing head gaskets in an otherwise functional and not-abused CRD. This is not a design flaw, this is a manufacturing flaw.
Not necessarily. Bolts can loosen when they are used in dynamic environments such as vibration, shock or thermal cycling - this is a design flaw. The correct installation spec may not have been provided - this is a design flaw. If you're correct and it is a manufacturing issue we can only hope that it's limited to a batch of engines.
Wouldn't you think the bolt torque would be the same for any directly bordering a cylinder? That is how they are supposed to be according to the book process. If the dynamic environment (which I admit could certainly be a factor) was the main cause, why would it only be the ones in the middle that I have found loose? Why not between #2 and #1? Or #3 and #4? This is something I cannot explain. This is also the first design I've ever heard about that has an issue like this. Design or manufacturing flaw, either way, it is something that should have been found in quality testing before general sale of the model.
You are going to get stochastic variation on installed bolt torques. Good manufacturing practice is to select procedures that guarantee minimum clamping force on all bolts without exceeding maximum clamping force on
any bolt. If VMM had used hardened and ground washers under the bolts, for example, they would have eliminated the galling and friction between the head and the bolt head that is one source of torque variation. They also would have reduced the deformation of the head bolt recesses that Geordi and I and others have seen. Some engines are undoubtedly going to get 16 good head bolt installs, perhaps the majority of them. But others won't, as has repeatedly been demonstrated. It is a crap shoot, due to the unpredictable nature of the bolts selected.
the really nice thing about the ARP studs is that you get predictable, reliable clamping force EVERY TIME from EVERY STUD. I am convinced that this modification is one of the two most important mods one can make to ensure proper engine function, right up there with dealing with the soot problem.