Just purchased 97 F-250 460; motor has ticking noise. Owners mechanic removed valve cvrs & states oil sludge; ran one engine flush. Still ticks. I checked oil once purchased, had two qts over full mark. I drained out two qts. Still ticks. Before proceeding w/possible valve job, any tricks to try?
If it's a few lifters clattering, I wouldn't get too excited right away. I had one car years ago that never ticked even after sitting for a week, but every time I changed oil, enough must have run out of the passages that one lifter would collapse and rattle for at least 30 miles before it finally quieted down.
Sludge won't prevent oil from getting to the lifters but it could keep a few from filling with oil right away. In the '80s it was somewhat common to add a quart of automatic transmission fluid to the oil a couple of days before you planned on changing the oil. That was a lot less expensive than the "mechanic-in-a-can" additives that do basically the same thing.
Overfull oil can cause the lifters to collapse too. The oil gets whipped up by the spinning crankshaft and aerates it. That air compresses and prevents the oil from separating moving parts. If it gets into a lifter, it can take a while to bleed out, especially on engines that send oil up through hollow push rods to the rocker arms.
Ford also had some trouble with the push rods wearing where they contact the rocker arms. Those will cause a clicking noise.
Be sure the engine is reaching normal operating temperature. Low temperature will help blowby condense in the oil, which is what causes sludge, rather than get drawn out and burned. I haven't changed the oil in my '88 Grand Caravan in over nine years and 80,000 miles, (that's abuse, not neglect), but there is no sludge in it. I have to add a quart about every 1500 miles and that helps to maintain at least some of the additives that normally wear out. The point is, it's blowby and low temperature, or a lot of short trip driving, that lead to sludge.