It's really hard to say at this point. Seems we both suspect injection,timing rates, yet with so many of these trucks on the road already, seems that theroy is weak. After cruiseing the net, and still questioning the dealers i visit, the amount of failures is very low. Food for thought, many years ago i worked as quality control for a steel foundry. We had a run of castings come back with stress cracks, from the heat they were subject to. We had produced hundreds of these for the customer in the past, with no issues. Long story short, after testing i found the nickel content on the batch of casting was very low. One key element missing in the metal, led to the cracking. Since the failure seems to involve the valve only, Perhaps it's isolated? On edit, i took another look at the discoloring of the valves. Seeing how you work on diesels every day, i'am sure you would agree that when you pull the head of a otherwise healthy running engine, the heads/valves typicaly have a light coating of black carbon on them. Wonder why this one has a whiteish, copperish look to it? hmmm, might be back to our original thoughts of timing/injection...Yes, the crack is on the valve only... The valve seats appear to be intact. While we are hoping that its an early release quality control issue. One can't help but wonder that maybe the emissions control strategy may be playing a significant factor in the valve fractures.
By altering injection rate, duration, and timing for emissions... . it would seem that it could very well add more stress/heat that initially anticipated by the design engineers. I don't pretend to be smarter than an engineer... just thorwing out possible scenarios. .
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