| Figured I would post these up for review of what I found and the remedy to the problem. Quick recap: While driving the car to the dyno, a mild tapping was noted in the engine bay, suspected it was just the cracked downpipe. Got to the dyno and made a few baseline pulls while getting the data acquisition setup configured, still noting the noise. Pulled car from dyno and drove home later that day and noted the noise still. Dropped the oil pan to inspect bearings and found rod bearing #4 just about to grenade the entire bottom end. The culprit: (Left bearing half is the upper bearing that takes the brunt of the power stroke - it is broken in two)
 The entire bearing set: left to right, 1 to 6, upper bearing to the left of each pair.
 The #4 crank journal: Note the amount of chamfering of the oil port. (two pictures) I'm not a fan of this chamfering process as it reduces the journal area in the wrong place. This oil hole is at the top of the journal where the piston exerts the maximum amount of load into the journal during its rotation. Looking at the wear pattern on the bearing, I am wondering if the journal was properly micrpolished after the chamfering process was done as chamfering leaves small raised edges that will eat a bearing alive.
 Journal after new bearing install and plastigauge clearance check. Measured clearance is 0.0015" and shows no sign of taper (even compression across the journal).
 Journal was micropolished with 1000 silicon carbide sandpaper cut into a strip as wide as the journal and the crank rotated by hand as the paper is band back and forth. This was just a preventive measure considering what happened to the original bearing and I didn't want to leave any chance of burrs damaging the new bearing. All of the rod bearings were replaced and plastigaguged to 0.0015" across the board. Everything was reassembled and I repaired the passenger downpipe which was pretty severely cracked on both pipes at the flange. Didn't want to have to listen to that noise while trying to make a determination if the knock is still present. The engine was started up and brought up to normal operating temperature. Dee noted that the oil pressure is higher than he has ever seen it. I made no change to the pressure relief valve in the oil pump while I was in there so we could see exactly what the difference would be, although we discussed taking the opportunity to shim the relief valve spring. I am wondering, based on his comment, exactly when the original bearing was beyond its clearance specification as Dee didn't have the Greddy oil PSI gauge in the car until some time after the new engine was installed. The fact that only one bearing was damaged really throws a kink in the idea that the engine was being pushed excessively via aggressive tuning. If it were detonating due to too lean of a fuel mixture or too much timing, or too much boost, we would see significantly more wear across the board on these bearings. It would have looked more like this collection of bearings, which came out of my old shortblock, of which I had detonated to heck and back during its life. 
I took the car out for a quick drive to see if things would hold together, but didn't have a chance to really get on it. We were pressed for time for me to get to the airport for my flight, so we will cross our fingers and see what happens later this week when I return to final tune the car on the dyno.
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Dee Ridgeway's rod bearing collection pictures >> - 
