i think the cam bear towers get their oil from the head which feeds the valve compensators ( lifters or facsimile thereof). if you look inside the journals there is an oil path from the bottom then up to the oil tube. also it appears to me that the rear of the cam could be open to atmosphere (hole) and with the holes in the oil tube venting to atmosphere as well that would or should be the end of the oil pressure system. i think the oil tubes are there more for the rockers than the bearings. although i wouldn't rule out they are design to assist in lubing the cam bearing journals.
the funny part is the cd manual (pg5-211) also implies that oil travel is thru the center of the cam. the cam is cast iron and i don't know how they would shake the core out and make the center clean enough to supply oil.
now i'm not certain about all this i'm just trying to figure out how the tube on mine plugged up just 1 little hole and none of the others. also when i miked the journals to compare to the new cam i was surprised to see the tolerance was still holding .0025 to .0045 inch. that tells me that my oil system on the journals was working just fine so i'm stumped as to why only 1 rocker bit the dust. oh well guess i should count myself lucky and as long as they run i shouldn't question why.
good luck on your project.
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