Noisy valve train: dangerous?

I’ve recently decided to keep my 94 Dakota (170K miles) long term. It has a vibrating noise you can feel and hear from the right valve cover. The mechanic said not to worry about it for now. Is a problem with the valve train likely to wreck the engine if not repaired? Are likely problems there easy to fix? (I’ve done “easy” jobs like brakes, water pumps, alternators.) Thanks for any advice!

Your next oil change…replace one quart of oil with a quart of Rislone. Do this for the next 2-3 oil changes. And change the oil every 2k miles during this period. See if that doesn’t clear up the noise.

I would be more concerned with a vibration than a tick
Valve trains can tick forever,but if things start vibrating I would want a exact diagnosis.

If nothing else, you might want to pull the valve cover and take a look around for loose nuts and bolts or anything that appears broken. All you’re out is a gasket. If this is a non-OHC design (push rods), you might get the specs on valve train clearances and adjustments and check that while you’re in there. Wouldn’t hurt.

It’s definitely a vibration, not the usual valve tick. I also noticed that it actually stops (rarely) at idle. When the vibration noise stops, it’s very easy to tell that it has stopped.

Aha! Found the problem: it was the PCV valve. Good valves have a little rattle but this thing was making a huge racket! Replaced the valve and voila – no more racket. Whew!