When I start the engine, the oil pressure is running only 1-2 bars. As the oil warms up, the oil pressure drops so the idiot light comes on. Same old story right? Here's where it gets fun. The engine is a 1971 that I rebuilt a year ago and am patiently waiting to drive. I put in new main and rod bearings (the crank was fine), new seals, timing chain (timing cover off 1970), tensioner and guides. I had the head (off a 1970) rebuilt with hardened seats and valves put in, new springs, new cam bearings, cam and lifters (went with hydraulic). Basically I gave it the works. When I first started to run the engine the new lifters failed to prime. Since I used gasket sealer on it, we thought that I clogged the oil port leading to the head, so I tore the engine back down and checked all the ports in the timing cover as well as the head, and everything checked out to be fine. The gasket sealer became a problem in the system, since it broke loose and I went through a series of cleaning my sump tube as it was getting clogged by the loose particles. After reassembly, the lifters still failed to prime, so I removed them and attempted to manually prime them to no avail. I read the threads here and went after all the solutions that were mentioned to fix this problem. OGTS alerted me to check the ball check in the oil filter area and sure enough the plug was worn out and oil could slip past, so I put in the ring that OGTS sells. I also replaced the oil pump cover with a new one and reworked the spring behind the ball as OGTS suggested. I fired up the engine and the results are the same. I am going to go back into the ball check on the side of the timing cover to make sure the ball is seating properly. I cannot look inside the hole or slip a finger in there to make sure no debris is holding it open. Any suggestions on how to check or clean it out? Also, the bottom of my oil pump gears are slightly scored. they look similar to a scored brake disc. Could this affect my oil pressure to the degree that I am suffering. Can I resurface them? Should I replace them, or would that be continuing to throw money at nothing? Could there be a problem in using the 1970 parts on the 1971 engine? I'm dying in the water here. Can anybody help?