I know what the inevitable suggestion will be...
My question to the crew is, IF it was a rocker arm, (I replaced the lifters [old ones had no wear signs] when we did the head gasket 20,000kms ago and the tick went away) is "it" more likely to begin to tick as soon as it starts or should it begin at op temp?
I think I know the answer, just looking for another possible way to rule out a slipped sleeve.
Side note, we it revs up it goes quiet and then begins to tick as it returns to regular idle as in video.
Cheers.

 

Have you ruled out vacuum and exhaust leaks?

 

Rocker arm ticks are super rare except in the case of low oil pressure due to walked cam bearing or broken oil pump (I have seen both). Test oil pressure first, then after confirming that monitor temperature using obd gauge and note temperature ticking starts at.

 

Right at 26 seconds, when it's revving up.

It's a tappet lifter

I agree, check oil pressure as a precautionary. Otherwise, get a set of lifters, soak them in oil overnight, and stick them in.

 

I agree with @User sounds like pushrods/lifters, typically at idle we have pretty low oil pressure as the engine wears, increase idle and oil pressure goes up. You could try the Liquid Moly lifter cleaner - it is not a solution but if things get quieter you at least know where the issue is.
I agreed with @Extinct generally rockers are not the source of the tick, unless they are very worn and gummed up or damaged

Also what weight oil are you running generally anything under a 10/## weight is too low

 

Almost never a lifter.

Here are the definitive steps to determining source of a tick:

1. Determine engine operating temperature ticking starts
   1. Over 180 degrees - install inline thermostat mod with 180 degree thermostat - problem solved.
   2. Under 180 degrees? Go to step 2
2. Does ticking go away over 1500 rpm?
   1. Check engine oil pressure at idle with engine at temperature ticking starts - oil pressure over 15psi?
      1. Yes - not low oil pressure, likely slipped liner
         1. Spray water on outside of engine block with engine running, does ticking stop?
            1. Yes - slipped liner
            2. No - stuck lifter.
      2. No - Low oil pressure is cause, determine source of low oil pressure
         1. Remove oil pan, inspect for walked cam bearing.
            1. Yes - replace cam bearing, hg and associated gaskets while apart
            2. No - Remove front cover and inspect oil pump for cracked gears - gears cracked?
               1. Yes - replace, do water pump and idler pulleys while apart
               2. No - do water pump and idler pulleys while apart. Consider 15w40 diesel motor oil to quiet lifters.

 

Thanks for the reply's everyone.
Appreciate you sharing your expertise.
@Dave03S - There are no exhaust leaks - promise...
@Richard Gallant - I've been using 15/40 Rotella for 10 years
@Extinct - Thank you for the breakdown.
- I did the 180 degree thermostat a few years ago as preventive
- As in the video it does go away when idle is held, that said, higher rpm would increase oil pressure, but I'll have it checked.

I did have a new oil pump and lifters done 15,000 miles ago along with the head gasket, the tick went away for a long while and now came back.
I actually work for a group that owns a Land Rover dealer and the older techs have said that the rocker arms used to be a problem area. The cap inside the arm for the push rod can be pushed in and out with a small screw driver.

The thing that throws me off was that it doesn't start ticking until it warms up... Especially with our typical low pressure... by the time it's at operating temp, the oil pressure will have increased, 15/40 is good and thick and my oil pan is super clean - no gunk.
Looks like I'll just have to pull it apart and see.

 

Oil pressure does not increase with temperature, it decreases, even with 15w40. Based on your service history it is a high probability that you have a slipped liner. You can test by spraying water on the block with the engine running at operating temperature. If the tick goes away it is a slipped liner.

 

Extinct - You are 100% correct on the oil temp and pressure, I meant ti infer rpm increases oil pressure...
I've been fighting the slipped liner thing proactively since I got this thing 11 years ago. Lower thermostat, right oil, all the things.... It's never overheated, I've never seen the temp gauge raise above middle (and I know it's a flawed gauge) but still it haunts me.
I'll try the water spray test and let you know.
Cheers!