Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
Your noise is most probably roller lifters starting to fail.
Very common in the LS engine.
The lower noise is also a concern.
Have you measured the oil pressure with an accurate gauge?
How many miles on this engine?
Wow, that is good mileage from one of these.
What oil did you refill the engine with this time?
Does the ticking sound come from one side of the middle of the engine?
Your engine have AFM (drops from 8 to 4 cylinders under cruise condition)?
Yes the roller lifter (cam follower) operates to pushrod then the rocker arm.
The oil is correct spec.
If you are keen you can remove the passenger rocker cover, get a feeler gauge of about .010, and push it between each rocker arm and the valve stem tip with the engine running.
When you find the one which is ticking, it will go quiet momentarily.
AFM is great on paper, but I have seen many failures from roller lifter failure.
Can be the the "zero lash part" of the lifter that normally gives quiet operation, can be roller wheel or axle failure which can give a squeak to tapping noise, can be a lifter rotated in the block which gives permanent AFM on that cylinder and hence permanent misfire.
Does throw a little oil, but the test only takes about 30 seconds or so at idle.
I set up a large "splash shield" or box cardboard or similar which absorbs some oil and keeps most of the inner guard components.
You are the 3rd customer I have had in the past few weeks with an AFM engine issue.
Hope this helps.
I hope my advice has been of assistance to you.