I just finished tearing apart my 292 to rebuild it this winter.One of my problems was slow oil to the right side rocker shaft.John Mummert mentioned that he has found that problem more often in the right side,Anyway,now I can see the problem.I can get a wire down from the top of the block into the centre cam bearing on the left no problem.The right side I cant do it from the top down or bottom up.It looks like more wear on the right side of the bearing or the bearing has turned slightly blocking most of the hole.If you are having a similar problem more with the right side than left this may be whats happened to yours.John Mummert mentioned that he thought it may be more wear on the right side of the bearing  due to direction of engine rotation(as I recall).Now to get on with rebuilding it!