It is definitely a "rod" knock. The knock is present at idle and louder when engine is "revved". Under a load (clutch released / brake on) the knock subsides somewhat. I was surprised to find insert bearings as the casting numbers on the block indicate a 1950-51 engine.
The engine was painted Blue, however. Might be from a Power Glide car? I will pull # 4 tomorrow (weather providing) and repost results. I just can't think that # 4 is the culprit - "snaps" from side to side on the shaft like the others.
Maybe the slight "tolerance" difference is causing the noise - a real puzzle for me. BW
