Cold-start engine knock mystery @198,000 mi (and engine condition generally)

No, but I do have more data.

Oil pressure (spec. ≥ 4.3 psi idle, 22 - 80 psi @ 2250 RPM): 44 psi @1280, 48 @ 2240.

I was prepared for some oil to escape when I removed the pressure switch, but none did. On the other hand, I had trouble with tool access to fully tighten the pressure-test hose (the 1/8-28 BSPT adapter in my test set is an elbow, so I had to thread that in first and then thread the 1/8-27 NPT tester hose into it, and at the angle where it ended up I couldn't effectively tighten it). So there was some oil dribbling out the whole time I was testing, so I didn't wait for full operating temp to get a number for idle RPM < 1280.

Cylinder leakage re-test. In January, out of curiosity, I tried a cleaning additive in the oil, running it for 3000 miles followed by a 3000 mile plain oil rinse. Using the same leakdown tester as in December, I now get:

	Cylinder	@90psi	%
1	1	88	2
2	3	87	3
3	4	88	2
4	2	87	3

Those numbers are improved over what I had in December. In the same period I also ran one dose of Techron in the fuel system, so it may be hard to assign credit to one additive or the other. The Techron may have cleaned valve sealing surfaces, or the oil additive may have cleaned the rings. The engine temp may have been different for this test than in December. But on the face of it, these numbers seem to show something improved.

There was no noticeable improvement in varnish under the valve cover.

The spark plugs look gorgeous, and all the same. There is no longer one of them with extra black fluff. I'll credit this probably to the fuel injector servicing.

In a lot of ways, this engine seems in very good health. But I can now see visible surface defects on the cam lobes, which I don't remember seeing in December. I have a bunch of phone pictures I don't have time to upload at the moment (and I'm not sure the defects will show up well because of glare from the flash). It has seemed that at least some of the noise has been valve train all along, and this seems to confirm it. But I still don't know if there is some other condition, like restricted oil to the valve train, contributing to the wear.

-Chap

Edit: update table in ancient post because XenForo keeps changing how tables work
Edit: make reference to earlier post into a link