There have been a number of reports about a mis-drilled rocker arm shaft oiling cross-hole drilled in the #4 camshaft journal. If this hole is not drilled in the correct location, the oil flow to the rocker arm shaft and the rocker arms will be substantially reduced or non-exsistant.
The best way to check a cam for the correct oil cross-hole placement is to use a cam bearing for the #4 location. Slide the bearing onto the rear cam journal and see if the holes in the bearing line-up to the cross hole in the cam. The holes will only line-up in one position.
One other way to checK is to mark the cam and engine block surfaces and check to see if the marks align during cam rotation.
If the hole does not allow oil to flow thru the cross-hole and bearing holes, the cam or bearing should be reworked. The cam journal can be grooved or the cross-hole's entrance elongated in order to get proper alignment. The bearing can also be grooved in a way that allows a flow path for the oil, even if there is no cross-hole in the cam.
Here is a drawing showing how the cross-hole is drilled.
One "work-around" fix to a rocker arm shaft that does not get oil is to drill and tap a separate oil feed hole into the lower rear cylinder head bolt hole. Use a piece of tubing to feed oil into that location and it will oil the rocker arm shaft.
DD
