I’ve run a lot of searches and tried to find an answer, but just can’t find anyone who has diagnosed this exact issue. Engine, a 1990 LB9, has about 110,000 miles. It starts fine and makes no bad sounds when cold at idle with 60+ psi oil pressure. Once at operating temperature, however, it randomly starts to slowly tick from what sounds like the passenger side valve cover (using a stethoscope). It may last a couple seconds or 20 seconds, goes away, and comes back. At the same time, oil pressure at idle has dropped to about 30-35 psi, whereas at cold idle and when RPMs increase it is at 60+ psi. As soon as you increase the RPMs the ticking stops and is never heard while driving. Is this a sticky lifter or something else? And is the drop in oil pressure at idle when warm normal?

 

'Sounds like a bad lifter to me, and 30-35 psi hot oil pressure at idle is plenty...

 

Thank you. Is this something that needs to be resolved now or can it wait for a while? I have taken the TPI runners and EGR off before (several times) but have never gone beyond that. And what all needs to, or is advisable to, be changed, presuming it is just a lifter going bad?

 

How are the valves adjusted right now?

 

Stock, as far as I know. I have not removed the valve covers. This will be new territory for me.

 

Try adjusting the valves. Don't jump to the conclusion that there are bad parts until you perform the regularly required maintenance.

 

Will do. Thanks for the advice.

 

I may need some education here. I thought hydraulic lifters prevented the need for valve adjustment?

 

They tend to have very long intervals between adjustments, but sometimes still do occasionally need a touch-up.

Of course it's also not impossible that as the OP does his thing, he may come across some failure or other; bad rocker, bent push rod, etc. First step though is to pop off the VCs and attempt to adjust. Then go from there.