I have a rebuilt 350 with a mild cam, Edelbrock 650 cfm carb, Powerhouse intake and a noisey gear drive. I am using Dakota Digital Gauges. I also have a high volume oil pump. Here is my problem, at idle the oil pressure drops between 12-17 psi and a rattling noise occurs. As soon as I begin to drive the pressure will go back up to 27-39 psi. It will remain constant along with the constant speed. I have followed the proper break-in procedures. The motor has approximately 42 miles on it now. As long as the rpm remains above 900 the pressure doesn't drop and the noise does not occur. Can someone tell me what is going on? Can someone also tell me what the idle rpm should be? I would also like to know what the oil pressure should be at? This is my first project and I am having a darn time figuring this thing out. The motor runs and sounds smooth, doesn't smoke, burn oil or do anything out if the norm with the exception of the low oil pressure if the rpm falls too low. Thanx guys.