Hello.
Olds 455, aluminium head, aluminium 7/16 1.6 roller rockers, hydraulic lifters.

Some ticking noise. Start valve adjustment and two valves adjust when adjustment screw is almost in end (upper valve in picture 1).
For test, start up the engine (ticking ended), and notice that two rockers don't have oil flow through the pushrod (picture 2).

Are those two hydraulic lifters somehow death? 2000 miles old Melling.
How critical it is? (would not like to start change of lifters in the middle of season).
Oiling problem is because of adjustment screw is so far out that oil cannot exit to rocker channel? Or could it be already from lifer ( can they be stuck)?
Would the easy fix be higher pushrod or is bad lifer somehow dangerous?

Picture 1


Picture 2

 

^^^^^^^^^^^ That would be my guess since the two that are turned almost the whole way in are the ones with no oil.

 

Mellling lifters? How did you arrive at the pushrod length?