1982 BMW 528e engine noise

Hello,
My car makes a noise like a loose fan belt or a chirping noise but when the car warms up the noise disappears. Removed all the fan belts and run the car and the noise was still there. I have to keep adding one quart of oil every six weeks, passes smog test, removed the cylinder head cover and adjusted the valves, while removing the spark plugs noticed on no. 1 spark plug well had plenty of oil so I suspect oil leak was due to worn cylinder head cover, adjusted valves in accordance with Bentley repair manual, replaced all plugs, by the way the engine was overhauled at 150000 miles. Engine runs great, just this noise is worrying me don't want it to get any worse, please HELP!