No oil getting pumped top end

1998 Pajero IO 1.8l DOHC that we recently torn down and changed the valve guide seals. The plugs were getting fouled out and was having lots of light blue smoke on a cold start. So did a small tear down and now there is no oil getting pumped to the top end of the engine. This started a few days after it was put back together. Any recommendations on a good place to start. Where would the oil getting pumped top end run into a possible blocked passage. So my question is where is a good place to look for the problem?