Not getting oil to all rockers

[Tennessee69]

Vehicle is a 1969 f100 with 300. 300 has casting numbers, I believe dates it as a 1966 block.

Heard ticking coming from motor, so I pulled valve cover. Saw that #1 exhuast rocker, #2 intake & exhuast and #3 exhuast rocker were not getting oil.

What I have done so far:
Pulled the rockers and push rods to check for clogs and they were clear.
Pulled oil pan and found a little slug, not much.
Change the oil pump since I was already in the pan, didn't change anything no oil to the same rockers.

Not sure where else to look for clogs, asking for any ideas.

 

[Fellro]

Could well be that the lifters are stuck internally. They will still go up and down like a solid tappet, but they will no longer have the hydraulic action.

 

[5.0Flareside]

lifters are clogged up.

 

[Tennessee69]

Thanx fellows,
Lifters had failed internally, changed them out and oil is following again.