oil passage blockage?

[threearmsinjune]

i need help with a small block 350 oiling issue. I have rebuilt the motor and have taken care to make sure everything fits correctly and that all holes and passages are aligned. When priming the oil system I found that the right top end system is not receiving oil. The left is fine. I believe there is a restriction in the internal oil passages but I am not sure what direction they are routed. I would like to blow air backwards through each passage to dislodge, but are the passages directional as far as oil flow? which end is pressurized from pump? any diagrams or experience would be helpful.

all plugs are in and I did not have distributor to prime pump. I used the old intermediate pump shaft.