BobBob S. said:If I am following your thinking and if the root cause is in the wear in the cam bearings, is this something that might be monitored via accurate oil pressure monitoring. Ie. A quality mechanical gage? Or, do you suspect that the condition will not show becuase of the pressure relief?
I finally think, see paragraph three, cam-bearing oil gallery pressure will be expressed as a percentage of the block pressure supplied to the mains. Bob you can just read three to see the answer to your question.
This all has so many factors that it is hard to pin this down to one or two simple statements. It has been pointed out to me before that the actual wear on the cam bearings is small. The only thing is, there seems to be a relationship between the wear and the final resting /running place of the cam over the oil slots / holes. So in one sense it is position of the camshaft that kills the oil flow that would pour over on the followers / lifters / tappets / lobes. Our health has things that affect it: diet, exercise, rest, stress, relationships. Which one is the root?
The guage thing is going to require at least two guages, one on the supply that the crankshaft sees, and one on the cam-bearing oil gallery. It will finally be probably expressed as a percentage of the higher number. I suspect that the pressure in the cam-bearing oil gallery gets higher when the cam covers the holes. Oil used, style of driving, climate, OCI everything plays a part, but you must have full oil supply to the followers to operate with the least wear.
In the good old days (sometimes now) worn cam-bearings would dump most of the oil pressure in an engine, but now, at times, there is restriction (either gallery size or a planned restriction) going to the cam bearings to maintain crank rod pressure after it (cam bearing wear) reaches a certain flow. Engineering has progressed in a lot of cases. Just stop here. The VW PD does not flow more oil with cam bearing wear, it flows less. Just backwards of all we normally think. You cover the oil holes and the pressure rises in the cam-bearing oil gallery. This pressure rise causes the followers to press harder on the cam, and flow less spillage to lubricate the folowers. Higher oil slot placement will help. The oil slot was just placed in a loaded area (loaded after slight wear).
I have to watch it or I just repeat it all again (I know I just did- sorry). I do not know if the oil pressure guages will tell the whole story. I just observed that new cam bearings changed the condition of my cam wear. I see signs of oil slot covering that is worse the more the cam bearing wear. Thanks to all those that posted and continue to post cam bearing wear pictures.
We need a head cut into 20 pieces so we can know the whole story. Where does the second guage need to tap in? Do we need to make a new tap hole? Or, we can just fix the bearings to operate like new bearings, for a longer time. The cams do not fail the first 25,000 miles US. They seem to slow the oiling, and at a mileage (that differs from person to person) rapid wear begins to accelerate. IMHO. We are watching cams now to see what the story is.