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Discussion Starter · #1 ·
I bought '66 C10 with a 250 six cylinder and manual transmission recently. It had been off the road in a shed for about 15 years.
While looking it over at the seller's, it was barely running and had a bad exhaust manifold-to-pipe leak which was very noisy. I could see that the engine didn't smoke, had good oil pressure, and no water in the oil or vice versa. After some carb and ignition work, and a new exhaust donut I got it running smoothly and quietly, but discovered it has a knock. Not too loud at idle, but definitely loud under load or revving up the engine.

Oil pressure is 1/2 to 3/4 on the stock dash gauge (I didn't connect a psi gauge)
Cold compression is 150 psi across all six cylinders
Warms up to temperature with no water leaks.
Valve train was fairly clean under the valve cover when I adjusted the valves.
No junk in the engine oil when I drained it or junk stuck to the drain plug.

I jacked up the engine and pulled off the oil pan expecting to find a loose rod bearing or discolored bearing caps. Because of the large suspension cross member, I can't really pull off all of the bearing caps, but I did pull the cylinder #1 rod cap and the bearing/crank looks pretty good.

The oil pan had only minor sludge on the bottom, however, when I started to wipe out the pan I found the items in the attached pictures.

A couple of the parts have "wipe" marks like perhaps they were a thrust "bearing" surface but they are not galled.

Any thoughts on what these parts are and if being in the pan instead of their former location could cause a knock?
 

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As you said thrust bearing...or maybe timing gears...so is the pan totally off, can you see anything...?
 

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Yes, oil pan is completely off, but I'm not seeing any visible damage to the crank or to the bottom of the pistons, and no perceived play in any of the bearings

Looking at the debris from the oil pan a little closer, the thinner pieces that have some shiny circular wear marks are steel. The two thicker parts at the top of the photo appear to be cast aluminum.

The bolt ends of the Camshaft Thrust Plate in the attached picture look suspiciously like one of the rounded pieces that I found in the oil pan. And the Camshaft gear can be fiber or aluminum which could explain the cast aluminium pieces.

I'm now thinking that perhaps one of the screws retaining the Camshaft Thrust Plate worked loose and hit the backside of the timing gear, causing the broken bits. Not sure why the failure of that thrust plate would make a knock.

Next step is to pull the engine and timing cover to investigate.
 

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To be honest with you , never been in a six cylinder, its only a guess on my part...!
 

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Is your timing cover aluminum by chance? If so they appear to be bolt hole bosses or something similar but the other parts look like hardened gasket material but you said they were steel correct?
 
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