After the busyness of the year end, we were finally able to get into the motor. Through careful disassembly, we were looking for any signs that might give indication or cause for the detonation. In the end there was nothing that was obvious to see, that could have obviously provoked the #6 rod to come through the case.
If there was an over-revved cause, I suspected we might see some impact marks from the valves on the crowns of the pistons - but there were no marks, the valves and the springs are still good. The bearings were all still good, as is to be expected from a motor with 11 500 miles on it.
What is noteworthy is that both ARP conrod bolts broke, and both still have the nuts attached to the bolt ends. One fell out the bottom of the case through the oil drain plug and the other conrod bolt end (with the nut still attached) got impaled into the inside of the case, and produdes a little through the outside.
The other item to note is that; at installation the ARP - 2000 conrod bolts were all a polished silver in color with black ARP nuts. When we disassembled the motor, 8 of the bolts were still silver, but 4 were now black. Not an oil tarnish that could wipe off. You can see the color changes in the photo's below.
All the ARP conrod bolts have been shipped to ARP for analysis. Im hoping to get conclusive remarks from ARP that can lead to a better understanding of the cause for bolt failure.
