*EDIT* Due to a vendor's misinterpretation of our intention, we are going to CLARIFY what we mean about what we mean by "life expectancy"...
VW's engineering fault with the cam bearing support that is difficult to overcome. The cam follower (lifter) bore cuts a radius that removes up to 1/2 of the cam bearing support on the the #2, and #4 bearings, with the #3 bearing support losing about 40% of the total bearing surface. This leaves the lower cam bearing, which is the loaded bearing, with the two ends of the bearing unsupported. The reduced support causes extra wear on the center of the bearing shells.
In order to correct the engineering, stiffer shells are the only solution within the parameters of the head design. It has not been practical to pursue alternate bearing designs, so we accept the wear potential. This is NOT an INCREASE in WEAR from the stock design. The cam bearing modifications were made to improve oiling to the CAM FOLLOWERS, with some expectation that wear to the lower bearing shell would be reduced.
Anyone who has removed a cam from a PD has seen the exact same wear pattern in the lower shells. Although the modification for redirect for the oil in the cam bearings is appropriate, and does DOUBLE the oiling to the cam followers, we have limited ability to correct the lack of support for the lower shell. The only thing we can do is provide correct oiling to the bearing. It is a fault in this engine that, at this time, has to be accepted.
As for our CAM Profile and Longevity:
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As of this last week, we have received a report of a cam and bearing set that has gone 275,000 miles with no symptoms of wear. THAT IS OUR GOAL and WE ARE ACCOMPLISHING OUR OBJECTIVE.
*END EDIT*
I thought I would give everyone an update about our cam bearings. We have so many out in the field now, what we can say that is good... we have a bare minimum of complaints. The design of the bearing support does not aid in the life expectancy. However, we do see that the major goal of the bearings; moving oil to the cam followers, is effective. Between the cam bearing mods, the cam mods and the use of proper oil and break-in, we feel we have improved the lot of the PD's.
Most recently, we have added tooling to our shop to take care of an occasional concern with warp in the cam journals. It does not happen as easily or readily as it has in the ALH or AHU, but we have found that the higher the motor is driven, the more likely the wear to the cam bearings. We will continue to work out solutions for issues.