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7/27/20: I started disassembling the engine and here is what I found under the main bearing caps.

First a little history: I was able to locate and contact the PO that had the engine rebuilt six years ago. He was more than happy to talk to me about the truck and told me some history about the engine rebuild. After the original rebuilt, he had a main bearing ceased up due to a bearing being too tight and the machine shop remedied it by adding .001” shims to all the main bearing caps. He had also experienced low oil pressure issue after the rebuild.

The first shim under the rear main is not .001” thick, but .009”. I had planned to Plastigauge all of the bearings and ordered a set on line last year. That’s when Murphy’s law came into effect. I went to use them and there wasn’t any plastic line in the package. Neither the green (.001”-.003”) or the red (.002”-.006”) that I ordered contained any gauge. I figured I could go to the “not so local” NAPA dealer 20 minutes away and buy what I needed. The only gauge they had was .001”-.003” so I settled for that.

I Plastigauged the rear main bearing and it is larger that the .003” the gauge is limited too. It just started to squeeze out but not measurable on the scale. I needed the red package. I stopped right there as I don’t think Plastigauge is going to tell me the story.

I was anticipating having to pull out a small shim, but when I encountered the .009” shim, that has me really perplexed. It would seem to me if they needed a little more clearance, why would they put a .009” shim in? At this point, I’m going to pull the crank and get proper mic readings. That way it will tell me what the real story is.