22R knocking when cold
 

Hey guys. My 85 Pickup is making a kind of knocking noise, sounds kind of like rod knock. But it's only doing it when its cold and accelerating in gear. definately related to engine rpm not speed so it can't be the drivetrain. Just revving the engine in neutral wont do it, and once the engines warmed up it stops completely. Its got 180k on the clock. Other than the knocking it runs perfectly. I just got the truck and it had some REALLY nasty looking oil in it. I changed it the first time and a lot of the nasty oil stayed in there, but after changing it the second time it has stayed clean. but the same knocking noise! any ideas? and is it something i should be worried about?

this is old but if u never figured it out it prob needs a valve adjustment