engine ticking sound

[Bored_2wd]

I've got a '93 ranger with the 4.0, about 150k miles on it. I've noticed a ticking at idle, it gets faster with the rpms. I recently had an oil change that put in dino oil instead of the synthetic I've been running. i'm going to switch back, it was a mistake on my part - i forgot to tell them. Anyway, any idea what is causing the ticking? Could it be valves or rocker arms? Am I approaching a rebuild?
--Bob

 

[BeauJ]

My '92 explorer did the same thing. I thought it was a lifter, but it ended up being my lower manifold gasket

 

[grafy]

My 91 did the same things. When I first got it I changed the oil and it was really sludged up in the pan ,had to clear the drain hole with a screw driver it was that bad. I flushed the engine a few times and the ticking would stop for a week or three which is about 700 miles, then the noise would return. It sounded like the lifters were ticking. I changed the oil every 1000 miles as I was freaked by all the sludge. But the ticking would return. I then switched to Mobil 1 syn and the ticking has not returned. hope this helps