273 rocker arm adjustment

ok, so i didnt realize this until now, but you can get the lifters out through the head without taking the intake manifold off, i used a magnet and pulled one of the lifters that wasnt compressing, put it on the bench to confirm that it wasnt compressing, then i took it part, didnt see anything wrong with it, put it back together and now it compresses....not sure whats going on there. (was not looking forward to pulling the top of the engine off)

as far as the adjustment goes, am i looking to tighten adjuster so the push rod doesnt havent any free play but not compressing the lifter piston correct? this is a fine line, also i am still confused about the cam card saying 0 lash, how do you use a feeler gauge without compressing the lifter, also not sure about the pre load either.

Have you guys added the banana grooves before? how did you go about doing that?