The oil flows through the holes in the cam to the heads when it is rotated to the correct position, as you eluded to. Some cams have a full groove on that #3 cam bearing to supply more oil to the top end.
Where and what is oil coming out of under the cylinders? Through the lifters? There could be an air pocket blocking the oil from getting to the back of the block. Have you tried removing the OP port feed and priming it?
Be aware that rotating a new motor over excessively can wipe off most of your cam lube prior to the initial firing and cam break-in sequence. If you leave the manifold off until your done priming the motor, you can reapply more lube.
