Today I put my engine on a stand. I got the oil pan and pump off. I was looking inside and shyt. I see bolt threads. Retrieved the bolt with a magnet and there is no head on it. (I'll have to check for the head inside.) Then I notice it's a main cap bolt. What's going on here? Turns out it's one of the bolts from the number 4 main cap. I took the caps off. One at a time and replaced them so as not to mix them up. The bearings all looked pretty much the same, a little scoring but not real bad. This engine has almost 300K on it and the oil pressure was about 45 @ warm idle & 65+ doing about 70 MPH. So, my questions are 1. How do you suppose this happened? 2. Do you think it's worth putting anything into this or get another engine? BTW, the bearings did their job. The journals look pretty good.