Hmmm, Can't tell for sure on the video but it looks like the pushrod is spinning but not moving up or down. The cam lobe will rotate the lifter every time it sweeps the bottom, if you have standard/hydraulic flat tappets. When you swapped the rocker and rod from the intake was there any wear on the bottom of the rod? Did you adjust the rocker with the engine running? When you pushed the rocker down with your finger did the rocker then move up and down? Are you sure the valve isn't stuck open. You could remove the rocker and tap the top of the valve with a dead blow mallet and see if the valve opens and then closes again. Only do this with the piston on the bottom of the stroke as to not hit the top of the piston with the valve. 'used to do it with running truck engines but they had gobs of clearance at TDC. Any oil coming out of the top of the rod?
If the rod, valve, spring and rocker are all good and adjusted correctly, one can only assume the problem is the camshaft or the lifter. The camshaft lobe may be worn down to next to nothing, the lifter may not be holding oil, or the lifter may be stuck in the lifter bore and not dropping back down with the lobe. The lifter may be cocked in a worn-beyond -limits lifter bore or maybe a piece of flashing or some other foreign matter is caught in there keeping the lifter up. That's kind of a long shot, I'd say a worn camshaft, but like I said I'm not an expert, these are just my opinions. Most likely someone with more knowledge of these matters will diagnose the cause for you.
