[peva]

"I'll be back." no pun intended . . .

A chiropractor I used to go to had a doormat at the entrance of her office that said "Glad to see your back!"

 

[peva]

Particularly since you haven't been able to find the source of the errant material, I would include on the list of possibilities that it was machining chips (perhaps sitting in a less visible recess) that weren't cleared and made it thru the assembly process.

I know that there were reports on the 300M forums of a certain period of production from which a bolus of some of the materials used in the sand casting process of the block was left in (or eventually accumulated and lodged in) a certain curvey and hard-to-reach area of the coolant galleys (leading to the heads or one of the heads) which led to very marginal cooling and a very-hard-to-diagnose overheating condition. (IIRC, the problem was only on 300M Special engines - not sure why that would be unless the Special blocks were made/processed on a different line.)

The cause of the problem wasn't discovered until finally one owner with the overheating problem discovered the debris in his engine when, having exhausted all other possible causes, stuck something into that passage, only to meet obstruction, and was able to dislodge some of the material (it was impacted in such a way that he could not clear the passage). Subsequently, from other owners that had the same pernicious overheating problem and checked and found the same condition, they were able to determine an apparent approximate production period during which it was a problem.

So it is conceivable that a one-off or percentile-basis occurrence of process debris could get thru any production line, and that you won that lottery. Just proposing that as a possibility. Even if that isn't the case, it may help you to lie to yourself that that is the case so you can quit racking/wracking your brain about where it came from.

 

[peva]

Pay attention to the details (positions of slots on ends of camshafts, positions of sprocket marks, positions of sprocket bolts relative to valve cover mounting planes) in the sketches from the FSM:

 

[peva]

I could be totally missing your point, but the chain's "links of color" don't matter. The relationship between the sprocket pairs is 100% what matters. IOW, 12 pins between the marks on the small sprockets, chain links of color can be anywhere. Those links of color move around from one rotation of the engine to the next. When re-using the old chain, often it's impossible to tell which links started out colored. Doesn't matter.

 

[peva]

I hear you about getting older. I used to love working on my cars. Now? Not so much.

 

[peva]

You give me too much credit. Yourself and others were talking about bearings. 👍