New to me '85 model. On start up after the car has been sitting for a couple days and yesterday after changing the oil, get a very loud noise from right valve cover that lasts maybe 2 seconds. My guess is it takes a couple seconds to pump the lifters up. Is this a common problem? Should I be concerned? Is there a check valve or something that needs to be fixed? At idle the oil pressure drops to 1 bar which should be normal, but seems to fluctuate much more than on my 300SE. Engine has 166K, from the amount of crud I cleaned out of the bottom of the oil filter bowl, not sure how dilegent the previous owners have been with regular oil changes etc.