[tharbert]

Chris: "With used components it is not (?) difficult to make a decision with regard to the amount of fatigue damage that has been accumulated unless the part has been used in very controlled conditions and monitored in terms of the stresses that have been generated in service. Many Aircraft components are monitored in this manner but the costs of producing the base line data to make this approach work is very high."

This is the crux of the matter, right? I wonder about "not"? As in, it's hard to determine whether to reuse a component unless the stress has been tracked in some manner? It seems you're discussing damage at a much smaller level than can be measured especially by DIYer's. Are there any tests that don't involve a lab to see stage 2 damage, something like a more sensitive magnaflux of some sort? Or, in your opinion, does Tippy have a point and that, say, a "T' engine's rods most probably won't have seen stresses that rise to stage 1/state 2 damage because the part is over-engineered for lower HP engines?