ISUZU 4ZE1 engine noise

[prclayton]

Here is my tail of whoa. It all started with the engine missing at 1000rpm-2500rpm, and lacked power. I did a compression test, and found cylinders 3 & 4 down. To cut a long story short, I had a burnt valve in 3 and aseating problem in 4. Otherwise eveyrthing else was OK. Now here is were the fun started. After re-installing the head, and setting the valve clearance, and checking valve train timing, I noticed a tick-tick-tick coming from the engine. Initially I thought this might be a bedding in problem, and let the car run for about two days before opening the tappet cover up. SOme of the tappet gaps had opened a bit, but it was minor. The tick-tick did not go away. I rechecked timing and clearance again, and refaced the tappets as they showed some signs of peening. So the noise is still there. What I have noticed in the past week, is the noise is getting louder, and picked something this morning that could be the problem. I beleive I may have an oil pressure problem. On initial start, the oil pressure reading goes to 8, and the engine is quiet, then hesitates, and drops to 4, then goes to 6, then settles back to 4 at about 2000 rpm. At idle it is at 2. The noise level changes with the oil pressure level, but I am not to sure that the oil pump is at fault, and was wondering if this is not a bypass valve problem. The engine has 160,000Km on it. Any ideas?