Does the copper tube go through the valve cover, or over it to a tapped hole in the cylinder head? There's a drilled/tapped hole at the center of the head that intersects the oil passages to the rocker arms. It's common to find a shade tree fix involving running a tube from the oil pressure port on the driver's side rear of the block to the threaded hole in the head. If somebody has drilled a hole in the valve cover and glued the tube in, you're dealing with Mr. Bad Wrench for sure! That fix needs to go away! It could starve the bearings for oil by bleeding too much away from the normal routing.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!