Question: Just recently rebuilt my 292 y-block that suffered a broken crankshaft. Had the heads reworked and the new crankshaft turned. Engine had new pistons and we installed new rings.  After rebuild on startup we noticed once engine got hot which was running it at idle for about 15 minutes, started seeing smoke come from the left bank or passenger side of car. Shut down the engine and pulled valve covers on both sides to check for oil flow. Had plenty oil on the driver side but none on the passenger side. After removing the rocker arm assembly, noticed a brass plug in the oil orifice hole with a very tiny hole drilled into it. Never had seen this before. Looked at several engines from different people and could not find any that had this insert into the head.  So the mechanic drilled this plug out and we started getting plenty of oil then. Now when the car is idling it smokes blue out the passenger side. Could the head gasket have blown in that short period of time running the engine?