Kind of hard to tell which of the sounds you're referring to but since this happens right after the oil was drained, I'd suspect some hydraulic lifters are bleeding down and refilling with air that takes a long time to work its way out. That will result in a light clattering noise that increases with increases in engine speed. It will sound like a typewriter.
The problem will be aggravated if you drain the oil then wait a long time, as in 15 - 30 minutes, to pour the new oil in. That gives the oil in the pump, pickup tube, and some passages time to run out and get replaced by air.
I had a '72 Dodge 340 that did that at every oil change. It always took about 100 miles for one lifter to quiet down. It doesn't hurt anything because the bearings are still getting fed pressurized oil. The difference though is Chrysler had passages to send oil to the rocker arms so they always got lubricated. Ford and GM send oil up through the hollow pushrods to lubricate the rocker arms. If the hole in the top of the lifter or the push rod is plugged, little oil will get to that rocker arm. That's also how the air bleeds out of the lifter.
At higher speeds there's going to be oil splashing around that will get onto other rocker arms to keep them lubricated. The fact that the noise quiets down eventually proves that there is some flow through the hollow push rods, so some oil is getting to the rocker arms.
The easiest fix is to start with a harsh detergent added to the oil just before it's changed to see if it will clear anything out. Next would be removing the push rods and feeding a thin wire through them to see if anything gets dislodged. If nothing is found, suspect a plugged bleed hole in a lifter, but it's standard procedure to replace all the lifters and the camshaft as a set when any one is replaced. They wear in together to form matched wear surfaces. Very often when just one lifter is replaced, it wipes out that cam lobe and the new lifter.
Be aware too that Ford had a well-known issue with wear on the ends of the push rods that caused a clicking noise. That noise did not go away. New push rods and rocker arms solved that noise.
Saturday, March 3rd, 2012 AT 7:52 AM