No oil at pushrods

Tweet

I have just completed a rebuild of a Chevy 305. After reinstalling it I was able to start it without any problems. However, after running it for about 5 minutes, I still did ot have any oil flowing through the pushrods. I know the pump is working since I removed the filter and pumped about 2 qts out of the engine in about 15 seconds. I am at a lose and have no other ideas. Do you have any