[chiphead]

I was afraid you'd say that.
It seems that the noise starts after the oil pressure builds.

The rockers clack for a few seconds and then go quiet, and about the same time the noise starts. So it may be related to oil pressure, like the load from the oil pump tries to move the cam forward/backward in the block. It could also be oil pump shaft or oil pump, but I would not expect that to be loudest in the front. It sounds like the lifters are hitting the valley pan, but this is HFT lifters and a stock replacement Butler pan, so there should be no chance of lifter to valley pan contact.

This is an engine of unknown history, it's a '69 400 transplanted into a '67 car. The car was restored in the early 1990s, so I assume the engine was rebuilt about the same time. Looks like a basic stock rebuild with a crane cam. I swapped the cam out for a 2802 because the crane cam was losing a lobe but I caught it early. Even had the stock oil baffles under the valve covers. Engine is very clean inside and has good compression, good oil pressure and runs strong. The only debris I found was some fine glitter in the head's oil returns, so I suspect the engine has been making metal for a long time. TH400 line pressure was VERY high 210PSI+, so I reduced line pressure to take some load off the thrust bearing.

Where does a stock windage tray usually fail? I have an inspection camera, I can snake it in while the cover is off and take a look around. At this point where should I look next?