Any Pontiac guys on here? Need insight.

I ran oil pump with drill on two diff engines with hydraulic lifters, one mopar, one small block Ford. In both cases oil visibly flowed to all 16 rocker arms without turning crank. And it was real obvious oil was flowing with valve covers off. I could see oil flowing out of push rods filling up heads and dripping down sides of engine.

Other thing I did was hook oil pressure gauge up to block while running drill.

Now if there is some other type of lifter that only oils when engine is running that I haven't seen.