Since stovebolt hydraulic lifters do not lube the rocker arms with hollow pushrods, air can get trapped in the lifter body and be very difficult to purge. That's the reason for the grooves in the bottom of the pushrod, and a vent hole or groove in the pushrod seat if there's not a weep hole in the center of the plunger. Dave's blog gives us some very useful procedures to make the lifters self-purging. Wherever an engine stops, a few valves will be open, with valve spring pressure trying to collapse the lifter. There might be a little bit of rattle on startup when those collapsed lifters are refilling, but it should go away in a few seconds, or a minute or two at most. Once the small block V8's and the 3rd. generation sixes started using hollow pushrods and oil flow through the lifters and pushrods to lube the top end, most of the hydraulic lifter problems disappeared. Unfortunately, it's difficult to modify a 235 or 261 engine to use tubular pushrods. (Not impossible- - - -I'm doing it on one engine I'm building).
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!