just to ad for future thread searchers, FWIW doing a running hot lash with the covers off or even using cut covers is completely un-necessary even a fool's errand IMO. been there done that & had an oil fire. for what?
it ridiculously easy to figure out how much plunger preload you're dialing per rotation / fraction of a rotation of the adjuster using basic math. further, working with pumped up lifters is not the way to go either. fresh, new, dry, empty or as close as you can get to this scenario lifters is the easiest way to achieve success the first time with no drama or even clean-up afterwards
but you need to develop a fine touch to identify zero lash, it's not that hard either. twist the pushrod back & forth between your index finger & thumb while turning the adjuster down in the tighten direction. at zero lash the pushrod will give very slight resistance, and i mean VERY slight. i think this is the point where many miss the zero lash & continue tightening the adjuster down to bottom the plunger, then add more rotation that lifts the valve off the seat preventing the engine from starting. Great Fireballs! frustration sets in and the hot running lash escapades begin
the same method works for shimming bolt down rockers, shim under the pedestal to achieve the same fraction of a turn of preload. easy peasy nice & cleany
it's not worth the mess or the risk of burning down your car and your house, not to mention good stock valve covers are getting scarce and worth many times their weight in scrap metal