Thanks Chris.....I had the valve cover off about 80K miles ago and it was pretty clean. I was using an oil catch can and was working fine until I noticed a reduced amount of oil after 4K miles. Went another oil change and very little was in the can. Turns out there was a small screen in the lid aside from the accumulating mesh and it clogged up.
I managed to clean the vacuum ports and restore PCV operation. The noise in the top has been reduced now but I believe I have something going on with #4.
I used a stethoscope on the #4 coil bolt and could hear a light knock but not that deep sounding. This knock went away when I disabled the #4 coil.
I would like to pull the pan and possibly replace the rod bearings...at least see what's going on.
The motor has 287K miles and really runs smooth and strong, compression is real good for the mileage, Number 4&5 have 190 PSI and the rest have 205-208 psi.
If I go with rod bearings, would OE GM bearings be a good choice or should I look elsewhere?
