Lifter rattle at start up

There were a couple of threads that went along with the video.
That motor got run on an engine dyno sounding like that prior to being installed in the car.

The cam and lifters got swapped out for something else....... noise went away.

At around that time frame there was another thread where someone had one of those lifters that wouldn’t pump up.
Got a replacement pair, problem solved.
Owner grinds the rivet down to disassemble collapsed lifter....... doesn’t find debris, but instead finds the feed hole going into the pressure chamber not drilled through.
No oil = no worky.