More thoughts...
I cleaned & inspected the rockers. Amazing good shape. No unusual wear patterns. Rollers have minimal wear including bearing. They all rotate smoothly with virtually no axial or radial free play that would indicate wear necessary to replace them. I expect this might be a bit controversial, but I am not planning to replace them and save $370.
This engine has 128k on the odo. We are only the 3rd owners. First owner had the majority of its life (down in GA - rust free

), the second owner put less than 30k miles on it if I recall the carfax records correctly. The second owner had disabled the EGR by unplugging the sensor. We discussed this when we bought it because I remember it being a bit of a gamble not knowing if that unplugged sensor was the only code lighting the check engine light. Regardless, he seemed to know why it was important to disable the EGR. I suppose it is possible the vehicle was run that way most of its life - maybe from the 1st owner. But I will say that the internals aren't as caked up with exhaust garbage as some of the photos I've seen. Its not pristine inside, but not horrible either. I think this just brings more proof that if you disable the EGR and keep on track with oil changes, rocker wear and failure is not inevitable.
Which I suppose brings me to the critical question of why did a valve fail? It seems that they are rare, at least by the experience noted here. I have seen records of at least one other on a different forum, but that was due to an overheat condition (or at least that was the reason cited). I somewhat question that reason because the stem was bent on that engine - clearly bent before breaking the end off. Here is the other one I found online:
http://www.ar15.com/forums/t_1_134/1482 ... oject.htmlRegardless, for the few that have broken a valve - what's going on? I am fairly certain this case was not an overheating condition. I was at the Jeep (after it died) within 15min and it was not hot/overheated. It was full coolant, no steam or any other signs of overheating. I have looked closely at the block, head and head gasket. No signs of leakage across/from any of the passages. Everything appears to have been sealed as it should be.
So what caused the #3 intake valve to just snap off? I am going to say it wasn't piston contact for 2 reasons. First, the engine was 'in time'. I was able to lock both of the cams & flywheel in the correct 90deg past TDC before disassembly. Second, I understand the rockers are designed to fail before breaking a valve. Clearly that did not happen. So it would seem that something else caused the end of the valve to just snap off.
What makes me concerned now is should I be suspect of the other valves in this head? Clearly that concern is moot if the machine shop tells me the head is scrap (taking it in later this AM). But if it isn't, do I just replace the one valve (or possibly both intake valves on #3 - or all 4 valves on #3)? Or do I take the precaution (and spend the $271) and replace all 16?